{"gene":"NFU1","run_date":"2026-06-10T05:19:52","timeline":{"discoveries":[{"year":1994,"finding":"NifU (A. vinelandii) is a homodimer containing one [2Fe-2S]2+/+ cluster per subunit, with complete cysteinyl coordination; the cluster has distinctive spectroscopic properties attributed to a novel arrangement of coordinating cysteine residues.","method":"Purification, UV/vis absorption, variable-temperature MCD, EPR, resonance Raman spectroscopy","journal":"Biochemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — multiple orthogonal biophysical methods on purified recombinant protein, foundational characterization replicated by subsequent studies","pmids":["7947754"],"is_preprint":false},{"year":2000,"finding":"NifU (A. vinelandii) interacts with NifS and a transient [2Fe-2S] cluster is assembled on NifU in vitro when incubated with ferric ion, L-cysteine, and catalytic NifS; approximately one transient [2Fe-2S] cluster is assembled per homodimer and is rapidly released upon reduction, consistent with NifU serving as an intermediate Fe-S cluster assembly scaffold.","method":"In vitro reconstitution with purified proteins, UV/vis and EPR spectroscopy","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro reconstitution with multiple spectroscopic validations, replicated conceptually in subsequent studies","pmids":["10639125"],"is_preprint":false},{"year":2000,"finding":"NifU (A. vinelandii) has a modular structure: the N-terminal domain contains a labile rubredoxin-like mononuclear iron-binding site (coordinated by Cys35, Cys62, Cys106) used for Fe-S cluster formation, and the C-terminal domain contains the permanent [2Fe-2S] cluster (coordinated by Cys137, Cys139, Cys172, Cys175); both sites are required for full physiological function.","method":"Primary sequence comparison, amino acid substitution/mutagenesis, optical and resonance Raman spectroscopy of recombinant full-length and truncated NifU fragments","journal":"Journal of biological inorganic chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — mutagenesis combined with spectroscopic characterization, multiple orthogonal methods","pmids":["10819462"],"is_preprint":false},{"year":2005,"finding":"Both the N-terminal (IscU-type) and C-terminal (Nfu-type) domains of NifU (A. vinelandii) can independently serve as scaffolds for [4Fe-4S] cluster assembly via NifS, with sequential assembly of [2Fe-2S] then [4Fe-4S] in the N-terminal domain; both domains transfer [4Fe-4S] clusters to apo-nitrogenase Fe protein. A conserved Asp37 in the N-terminal domain plays a critical role in cluster transfer.","method":"In vitro NifS-mediated Fe-S cluster assembly on full-length and truncated NifU, UV-vis and Mössbauer spectroscopy, analytical studies, mutagenesis, apo-nitrogenase activation assay","journal":"Biochemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — reconstitution, Mössbauer spectroscopy, mutagenesis, and functional transfer assay in one rigorous study","pmids":["16185064"],"is_preprint":false},{"year":2004,"finding":"Both the N-terminal (IscU-type) and C-terminal (Nfu-type) domains of NifU (A. vinelandii) can separately participate in nitrogenase-specific Fe-S cluster formation in vivo, with the N-terminal domain having the dominant function; this was supported by in vitro cluster assembly and transfer assays activating apo-nitrogenase Fe protein.","method":"Amino acid substitution genetics in A. vinelandii, in vitro Fe-S cluster assembly and transfer to apo-nitrogenase Fe protein","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1–2 / Moderate — combined in vivo genetic and in vitro biochemical approaches in single focused study","pmids":["14993221"],"is_preprint":false},{"year":2011,"finding":"NFU1 functions as a late-acting, substrate-specific maturation factor for a subset of mitochondrial Fe-S proteins: RNAi depletion of NFU1 in human cells markedly decreases lipoic acid synthase (LAS) activity and, consequently, pyruvate dehydrogenase complex (PDHC) activity, and reduces succinate dehydrogenase (complex II) amount, but does not affect other Fe-S proteins tested. In contrast, ISCU depletion severely affects all tested Fe-S proteins. Yeast Nfu1 deletion phenocopies this selective defect (reduced lipoylation and SDH activity).","method":"RNAi knockdown in human cells, enzymatic activity assays (LAS, PDHC, SDH), lipoic acid quantification, yeast NFU1 deletion, functional complementation with patient missense mutant protein","journal":"American journal of human genetics","confidence":"High","confidence_rationale":"Tier 2 / Strong — clean KD in human cells plus yeast KO with orthogonal biochemical readouts, replicated across two organisms","pmids":["22077971"],"is_preprint":false},{"year":2011,"finding":"Mitochondrial isoform of NFU1 (but not cytosolic isoform) is required for proper assembly of Fe-S centers needed for maturation of lipoate-containing 2-oxoacid dehydrogenases and respiratory chain complexes I, II, and III; retroviral transduction of the mitochondrial NFU1 isoform restores both functions in patient fibroblasts.","method":"Retroviral vector complementation of patient fibroblasts with isoform-specific NFU1 constructs, measurement of respiratory chain and oxoacid dehydrogenase complex activities","journal":"American journal of human genetics","confidence":"High","confidence_rationale":"Tier 2 / Moderate — isoform-specific complementation rescue with multiple biochemical readouts, single lab","pmids":["21944046"],"is_preprint":false},{"year":2016,"finding":"Human NFU1 protein structure was determined for both N- and C-terminal domains by NMR; SAXS data show full-length apo-NFU1 is monomeric, while two apo-NFU1 subunits coordinate one [4Fe-4S] cluster to form a cluster-linked dimer; holo-NFU1 ([4Fe-4S]-loaded) exists as a trimer of dimers with N-terminal regions forming a tripartite interface. Holo-NFU1 can activate apo-aconitase.","method":"NMR spectroscopy, small-angle X-ray scattering (SAXS), size-exclusion chromatography, apo-aconitase activation assay","journal":"Structure","confidence":"High","confidence_rationale":"Tier 1 / Moderate — NMR structure combined with SAXS and functional validation in single rigorous study","pmids":["27818104"],"is_preprint":false},{"year":2016,"finding":"Yeast Nfu1 physically interacts with components of the ISA [4Fe-4S] assembly complex and with client proteins requiring [4Fe-4S] clusters (e.g., lipoic acid synthase, respiratory chain subunits); Nfu1 functions in a late step of [4Fe-4S] cluster biogenesis and its function is of heightened importance during oxidative metabolism. Bol3 (yeast BOLA3 homolog) functions with Nfu1 at this late step to facilitate Fe-S transfer to client proteins.","method":"Genetic studies in yeast, proteomic protein-protein interaction studies (physical interaction with ISA complex and client proteins)","journal":"eLife","confidence":"High","confidence_rationale":"Tier 2 / Moderate — genetic epistasis plus proteomic interaction studies, yeast model, multiple orthogonal methods","pmids":["27532773"],"is_preprint":false},{"year":2017,"finding":"The disease-causing Gly208Cys substitution in NFU1 increases protein dimerization propensity and perturbs secondary structure, which severely impairs the ability of mutant NFU1 to accept an Fe-S cluster from physiologically relevant donor sources, thereby blocking downstream cluster trafficking. The additional cysteine at 208 does not itself serve as a cluster ligand.","method":"In vitro protein stability assays, analytical ultracentrifugation/oligomeric state analysis, circular dichroism, Fe-S cluster transfer assays, mutagenesis of cluster-binding site residues","journal":"Journal of molecular biology","confidence":"Medium","confidence_rationale":"Tier 1 / Weak — in vitro mutagenesis and cluster transfer assays, single lab","pmids":["28161430"],"is_preprint":false},{"year":2017,"finding":"The disease-causing Gly189Arg substitution in NFU1 increases flexibility, decreases stability, and shifts the monomer–dimer equilibrium toward monomer, impairing the protein's ability to receive an Fe-S cluster from physiological donor proteins.","method":"In vitro structural analysis, thermal stability assays, analytical ultracentrifugation, Fe-S cluster transfer assays","journal":"The FEBS journal","confidence":"Medium","confidence_rationale":"Tier 1 / Weak — in vitro biochemical and biophysical analysis, single lab","pmids":["28906594"],"is_preprint":false},{"year":2017,"finding":"Mutagenesis of the CXXC cluster-binding motif residues of NFU1 established that the Gly208Cys substitution does not directly coordinate the Fe-S cluster but instead causes global structural alterations that change the oligomerization state and result in MMDS1 disease phenotype.","method":"Site-directed mutagenesis of cluster-binding site and Gly208Cys background, spectroscopic cluster coordination analysis, oligomerization assays","journal":"The FEBS journal","confidence":"Medium","confidence_rationale":"Tier 1 / Weak — mutagenesis with spectroscopic readout, single lab study","pmids":["28906593"],"is_preprint":false},{"year":2020,"finding":"Human mitochondrial ISCU2 (ISCU) and ISCA1 are the direct donors of Fe-S clusters to NFU1: ISCU[4Fe-4S] (but not ISCU[2Fe-2S]) transfers its cluster to apo-NFU1 in vitro. NFU1 interacts with both ISCU2 and ISCA1, and the interaction site maps to a conserved hydrophobic patch at the end of the C-terminal alpha-helix of NFU1. Mutagenesis of this interaction site blocks Fe-S cluster acquisition by NFU1 and impairs downstream lipoylation. Ferredoxin 2 aids [4Fe-4S] formation on NFU1.","method":"NMR spectroscopy, SAXS, isothermal titration calorimetry (ITC), in vitro Fe-S cluster transfer assays, site-directed mutagenesis, monitoring of downstream client protein abundance","journal":"Journal of structural biology / Human molecular genetics","confidence":"High","confidence_rationale":"Tier 1 / Strong — two independent studies (PMID 32151725 and PMID 32776106) using reconstitution, NMR/SAXS, ITC, and mutagenesis confirming same interaction and transfer mechanism","pmids":["32151725","32776106"],"is_preprint":false},{"year":2021,"finding":"ISCA1 is the key mediator of [4Fe-4S] cluster transfer to NFU1: ISCA1 interacts with both ISCA2 and NFU1, but ISCA2 and NFU1 do not interact with each other directly. ISCA1 promotes formation of a transient ISCA1-ISCA2-NFU1 ternary complex, and through its specific interaction with the C-terminal cluster-binding domain of NFU1, drives [4Fe-4S] cluster transfer from the ISCA1-ISCA2 assembly complex to NFU1.","method":"NMR spectroscopy-based structural study, protein-protein interaction mapping, [4Fe-4S] cluster transfer assays","journal":"Journal of molecular biology","confidence":"High","confidence_rationale":"Tier 1 / Moderate — NMR structural analysis with functional cluster transfer assays, multiple orthogonal methods in single rigorous study","pmids":["33711344"],"is_preprint":false},{"year":2022,"finding":"Human NFU1 forms a tight complex with human lipoyl synthase (LIAS) in vitro and efficiently restores the auxiliary [4Fe-4S] cluster of LIAS during catalytic turnover, enabling multiple-turnover lipoyl synthesis. BOLA3 has no direct effect on Fe-S cluster transfer from NFU1 or GLRX5 to LIAS. ISCA1 and ISCA2 can also enhance LIAS turnover but only slightly.","method":"In vitro complex formation assay, multiple-turnover lipoyl synthase activity assay with purified proteins, comparison with BOLA3, GLRX5, ISCA1, ISCA2","journal":"ACS bio & med chem Au","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro reconstitution of complex formation plus functional catalytic assay demonstrating cluster regeneration, single lab with orthogonal methods","pmids":["36281303"],"is_preprint":false},{"year":2023,"finding":"NFU1 (via the ISCA1-NFU1 node) is required for insertion of the [4Fe-4S] cluster into the mitoribosome assembly factor METTL17; fibroblasts from NFU1-mutant patients show attenuation of mitochondrial protein synthesis, revealing a previously unrecognized role of NFU1 in mitoribosome biogenesis.","method":"Silencing of Fe-S cluster biosynthetic/delivery factors, analysis of mitoribosome stability, mitochondrial protein synthesis assays in patient fibroblasts","journal":"Nucleic acids research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic silencing plus patient fibroblast biochemical analysis, multiple readouts, single lab","pmids":["37823603"],"is_preprint":false},{"year":2023,"finding":"Structural plasticity of NFU1 domains is crucial for partner recognition and [4Fe-4S] cluster transfer: SAXS and paramagnetic NMR reveal structural models of ISCA1-ISCA2, ISCA1-ISCA2-NFU1, and ISCA1-NFU1 complexes showing the N-terminal domain of NFU1 acts as a modulator of cluster transfer, and the terminal stable [4Fe-4S]-containing species is the ISCA1-NFU1 complex.","method":"SEC-coupled SAXS, paramagnetic NMR, structural modeling of apo and holo complexes","journal":"Journal of molecular biology","confidence":"Medium","confidence_rationale":"Tier 1 / Weak — SAXS and NMR structural data, single lab, no mutagenesis confirmation of N-domain modulator role","pmids":["37211204"],"is_preprint":false},{"year":2003,"finding":"HIRIP5 (human NFU1/CGI-33) interacts specifically with the Lafora disease protein laforin both in vitro and in vivo; laforin uses its N-terminal CBD-4 domain to interact with the C-terminal NifU-like domain of HIRIP5/NFU1. Laforin dephosphorylates HIRIP5 in vitro, identifying NFU1 as a laforin substrate.","method":"Yeast two-hybrid screen, in vitro and in vivo co-immunoprecipitation, in vitro phosphatase assay","journal":"Human molecular genetics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reciprocal in vitro and in vivo interaction assays plus in vitro phosphatase activity, single lab","pmids":["12915448"],"is_preprint":false},{"year":2001,"finding":"Human HIRIP5 (NFU1) interacts with the HIRA protein in yeast two-hybrid and in vitro protein interaction experiments; HIRIP5/NFU1 is implicated in iron metabolism in mitochondria based on homology to yeast NFU1.","method":"Yeast two-hybrid screen, in vitro protein interaction assay","journal":"Biochimica et biophysica acta","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single yeast two-hybrid and in vitro pulldown, no functional mechanistic follow-up for the HIRA interaction","pmids":["11342215"],"is_preprint":false},{"year":2023,"finding":"C. elegans patient-specific nfu-1 variants (Gly147Arg and Gly166Cys, orthologs of human MMDS1 mutations) cause allele-specific dysfunction of acetylcholine signaling at neuromuscular junctions: Gly147Arg causes hypersensitivity to acetylcholine rescued by knockdown of acetylcholine release, while Gly166Cys causes predominantly postsynaptic acetylcholine hypersensitivity.","method":"C. elegans patient-variant knock-in strains, acetylcholine sensitivity assays, RNAi knockdown rescue","journal":"Disease models & mechanisms","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — defined cellular/synaptic phenotype with genetic rescue in a model organism, single lab","pmids":["36645076"],"is_preprint":false},{"year":2020,"finding":"Rats carrying the human NFU1 G206C mutation (equivalent to human G208C, introduced by CRISPR/Cas9) show decreased expression and activity of mitochondrial Complex II, markedly decreased pyruvate dehydrogenase activity, and decreased lipoate binding, confirming NFU1's role in Fe-S cluster delivery to Complex II and lipoic acid synthase in vivo. Male sex partially compensates via increased ISCU expression and complex IV activity.","method":"CRISPR/Cas9 knock-in rat model, mitochondrial complex activity assays, pyruvate dehydrogenase activity, lipoate binding analysis, protein expression studies","journal":"American journal of respiratory cell and molecular biology","confidence":"High","confidence_rationale":"Tier 2 / Moderate — in vivo humanized knock-in model with multiple biochemical readouts confirming mechanism from cell culture studies","pmids":["31461310"],"is_preprint":false}],"current_model":"Human NFU1 is a mitochondrial late-acting [4Fe-4S] cluster carrier protein that receives its [4Fe-4S] cluster from ISCU2 (which transfers the cluster as ISCU[4Fe-4S]) and from the ISCA1-ISCA2 complex via a transient ISCA1-ISCA2-NFU1 ternary complex orchestrated by ISCA1, then delivers the cluster to a specific subset of mitochondrial client proteins—most notably lipoic acid synthase (LIAS), succinate dehydrogenase (complex II), and the METTL17 mitoribosome assembly factor—thereby supporting lipoylation of pyruvate dehydrogenase, α-ketoglutarate dehydrogenase, and the glycine cleavage system, as well as respiratory chain assembly; loss-of-function mutations cause Multiple Mitochondrial Dysfunctions Syndrome 1 (MMDS1) characterized by combined defects in lipoic acid-dependent enzymes and respiratory chain complexes."},"narrative":{"mechanistic_narrative":"NFU1 is a late-acting mitochondrial [4Fe-4S] cluster carrier that delivers clusters to a defined subset of client proteins, supporting lipoic acid-dependent metabolism and respiratory chain assembly [PMID:22077971, PMID:21944046]. The protein is modular, built from an N-terminal IscU-type domain and a C-terminal Nfu-type cluster-binding domain, a architecture first defined in the bacterial ortholog NifU where the two domains independently serve as scaffolds for sequential [2Fe-2S]/[4Fe-4S] assembly and cluster transfer [PMID:7947754, PMID:10819462, PMID:16185064]; human apo-NFU1 is monomeric, coordinates one [4Fe-4S] cluster across two subunits as a cluster-linked dimer, and assembles into a holo trimer-of-dimers competent to activate apo-aconitase [PMID:27818104]. NFU1 receives its cluster from upstream donors: ISCU2 in its [4Fe-4S] form transfers cluster to apo-NFU1, with ferredoxin 2 aiding cluster formation, and the interaction maps to a conserved hydrophobic patch on the NFU1 C-terminal helix [PMID:32151725, PMID:32776106]. ISCA1 orchestrates an alternative route, bridging ISCA2 and NFU1 in a transient ISCA1-ISCA2-NFU1 ternary complex that resolves to a stable [4Fe-4S]-loaded ISCA1-NFU1 species [PMID:33711344, PMID:37211204]. NFU1 then matures specific clients: it forms a tight complex with lipoyl synthase (LIAS) and regenerates the auxiliary [4Fe-4S] cluster consumed during lipoyl synthesis, enabling multiple-turnover catalysis [PMID:36281303], and the ISCA1-NFU1 node inserts the [4Fe-4S] cluster into the mitoribosome assembly factor METTL17 [PMID:37823603]. Loss of NFU1 selectively impairs lipoylation of 2-oxoacid dehydrogenases (pyruvate dehydrogenase, α-ketoglutarate dehydrogenase) and reduces succinate dehydrogenase/complex II and other respiratory chain activities without globally affecting all Fe-S proteins [PMID:22077971, PMID:21944046, PMID:31461310]. Disease-causing missense mutations (e.g., Gly208Cys, Gly189Arg) destabilize the protein and shift its monomer-dimer equilibrium, blocking cluster acquisition from physiological donors rather than acting through direct cluster ligation, causing Multiple Mitochondrial Dysfunctions Syndrome 1 [PMID:28161430, PMID:28906594, PMID:28906593, PMID:31461310].","teleology":[{"year":1994,"claim":"Establishing that the NifU scaffold carries a spectroscopically distinct cysteine-coordinated Fe-S cluster defined the founding biochemical identity of the NFU protein family.","evidence":"Biophysical characterization (UV/vis, MCD, EPR, resonance Raman) of purified A. vinelandii NifU homodimer","pmids":["7947754"],"confidence":"High","gaps":["Bacterial ortholog only","Did not define the modular domain organization","No connection to human mitochondrial clients"]},{"year":2000,"claim":"Reconstitution showed NifU acts as a transient Fe-S assembly scaffold downstream of the cysteine desulfurase, framing the family as cluster intermediates rather than terminal cofactor proteins.","evidence":"In vitro reconstitution of NifU with NifS, ferric ion and L-cysteine, monitored by UV/vis and EPR","pmids":["10639125"],"confidence":"High","gaps":["Bacterial system","Did not identify downstream cluster acceptors","Mechanism of release inferred from reduction sensitivity"]},{"year":2000,"claim":"Mapping NifU's two cluster-binding sites to distinct N- and C-terminal domains established the bilobed architecture later recapitulated in human NFU1.","evidence":"Sequence comparison, mutagenesis of coordinating cysteines, and Raman/optical spectroscopy of NifU fragments","pmids":["10819462"],"confidence":"High","gaps":["Functional division of labor between domains not resolved","Bacterial protein"]},{"year":2005,"claim":"Demonstrating both NifU domains assemble and transfer [4Fe-4S] clusters to apo-nitrogenase clarified that the family delivers higher-order clusters, not just [2Fe-2S], and identified a conserved Asp critical for transfer.","evidence":"In vitro NifS-mediated assembly, Mössbauer spectroscopy, mutagenesis, apo-nitrogenase activation assays (with in vivo genetic support from prior work)","pmids":["16185064","14993221"],"confidence":"High","gaps":["Nitrogenase-specific clients in bacteria","Does not address mitochondrial client specificity"]},{"year":2011,"claim":"Defining NFU1 as a substrate-specific late-acting maturation factor explained why its loss produces a selective biochemical signature—lipoylation and complex II defects—rather than the global Fe-S failure seen with ISCU.","evidence":"RNAi in human cells and yeast deletion with LAS/PDHC/SDH activity and lipoate assays, plus isoform-specific retroviral complementation of patient fibroblasts","pmids":["22077971","21944046"],"confidence":"High","gaps":["Direct cluster donors and acceptors not yet biochemically identified","Mechanism of client selectivity unknown"]},{"year":2016,"claim":"Structural determination of human NFU1 resolved its oligomeric states and showed holo-NFU1 is competent to activate an apo Fe-S enzyme, providing a structural basis for cluster carriage.","evidence":"NMR domain structures, SAXS oligomeric analysis, SEC, and apo-aconitase activation assay; plus yeast genetic/proteomic interactions with the ISA complex and BOLA3 homolog Bol3","pmids":["27818104","27532773"],"confidence":"High","gaps":["Donor-to-NFU1 transfer mechanism not yet mapped at residue level","BOLA3/Bol3 functional contribution inferred genetically"]},{"year":2017,"claim":"Biophysical dissection of MMDS1 mutations established that pathogenicity arises from destabilization and altered oligomerization that block cluster acceptance, not from disrupted cluster ligation.","evidence":"In vitro stability, analytical ultracentrifugation, CD, and Fe-S transfer assays on Gly208Cys and Gly189Arg variants with cluster-site mutagenesis","pmids":["28161430","28906594","28906593"],"confidence":"Medium","gaps":["Single-lab in vitro work","Donor identity not defined in these studies","In vivo consequences inferred"]},{"year":2020,"claim":"Identifying ISCU2 and ISCA1 as direct cluster donors and mapping the interaction interface defined the upstream half of the NFU1 trafficking pathway.","evidence":"NMR, SAXS, ITC, in vitro [4Fe-4S] transfer assays, mutagenesis of the C-terminal hydrophobic patch, with ferredoxin 2 supporting cluster formation; plus humanized G206C knock-in rat confirming complex II/PDH/lipoate defects in vivo","pmids":["32151725","32776106","31461310"],"confidence":"High","gaps":["Relative in vivo contribution of ISCU2 vs ISCA1 routes unresolved","Sex-dependent compensation mechanism only partially explained"]},{"year":2021,"claim":"Showing ISCA1 bridges ISCA2 and NFU1 in a transient ternary complex established the molecular choreography of cluster handoff to NFU1.","evidence":"NMR structural study, interaction mapping, and [4Fe-4S] transfer assays of ISCA1/ISCA2/NFU1","pmids":["33711344"],"confidence":"High","gaps":["Kinetics of ternary complex resolution not quantified","Structural models lack high-resolution validation"]},{"year":2023,"claim":"Direct LIAS complex formation/cluster regeneration and METTL17 cluster insertion defined NFU1's terminal client-delivery functions, expanding its role to mitoribosome biogenesis.","evidence":"In vitro LIAS multiple-turnover lipoyl synthesis assay; silencing and patient-fibroblast mitochondrial translation/mitoribosome stability assays; plus SAXS/paramagnetic NMR models defining the stable ISCA1-NFU1 endpoint","pmids":["36281303","37823603","37211204"],"confidence":"Medium","gaps":["N-domain modulator role lacks mutagenesis confirmation","BOLA3 found dispensable for LIAS transfer, contrasting earlier genetic data","METTL17 study single lab"]},{"year":null,"claim":"How NFU1 achieves client selectivity—distinguishing LIAS, complex II, and METTL17 from other Fe-S apoproteins—remains mechanistically undefined.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No structural model of an NFU1-client transfer complex","Determinants of client discrimination unknown","Role of accessory factors in selectivity unresolved"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140104","term_label":"molecular carrier activity","supporting_discovery_ids":[5,12,14]}],"localization":[{"term_id":"GO:0005739","term_label":"mitochondrion","supporting_discovery_ids":[5,6]}],"pathway":[{"term_id":"R-HSA-1430728","term_label":"Metabolism","supporting_discovery_ids":[5,6,20]},{"term_id":"R-HSA-1852241","term_label":"Organelle biogenesis and maintenance","supporting_discovery_ids":[15]}],"complexes":["ISCA1-ISCA2-NFU1 ternary complex","ISCA1-NFU1 complex","NFU1-LIAS complex"],"partners":["ISCU","ISCA1","ISCA2","LIAS","METTL17","BOLA3","FDX2","HIRA"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q9UMS0","full_name":"NFU1 iron-sulfur cluster scaffold homolog, mitochondrial","aliases":["HIRA-interacting protein 5"],"length_aa":254,"mass_kda":28.5,"function":"Iron-sulfur cluster scaffold protein which can assemble [4Fe-4S] clusters and deliver them to target proteins","subcellular_location":"Mitochondrion; Cytoplasm, cytosol","url":"https://www.uniprot.org/uniprotkb/Q9UMS0/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/NFU1","classification":"Not Classified","n_dependent_lines":170,"n_total_lines":1208,"dependency_fraction":0.14072847682119205},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/NFU1","total_profiled":1310},"omim":[{"mim_id":"620938","title":"SPASTIC PARAPLEGIA 93, AUTOSOMAL RECESSIVE; SPG93","url":"https://www.omim.org/entry/620938"},{"mim_id":"615330","title":"MULTIPLE MITOCHONDRIAL DYSFUNCTIONS SYNDROME 3; MMDS3","url":"https://www.omim.org/entry/615330"},{"mim_id":"615316","title":"IRON-SULFUR CLUSTER ASSEMBLY FACTOR IBA57; IBA57","url":"https://www.omim.org/entry/615316"},{"mim_id":"614299","title":"MULTIPLE MITOCHONDRIAL DYSFUNCTIONS SYNDROME 2 WITH HYPERGLYCINEMIA; MMDS2","url":"https://www.omim.org/entry/614299"},{"mim_id":"613183","title":"BOLA FAMILY MEMBER 3; BOLA3","url":"https://www.omim.org/entry/613183"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Cytosol","reliability":"Supported"},{"location":"Nucleoplasm","reliability":"Additional"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/NFU1"},"hgnc":{"alias_symbol":["CGI-33","NifU","NIFUC"],"prev_symbol":["HIRIP5"]},"alphafold":{"accession":"Q9UMS0","domains":[{"cath_id":"3.30.1370.70","chopping":"63-148","consensus_level":"medium","plddt":95.132,"start":63,"end":148},{"cath_id":"3.30.300.130","chopping":"169-241","consensus_level":"medium","plddt":93.5827,"start":169,"end":241}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9UMS0","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q9UMS0-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q9UMS0-F1-predicted_aligned_error_v6.png","plddt_mean":78.94},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=NFU1","jax_strain_url":"https://www.jax.org/strain/search?query=NFU1"},"sequence":{"accession":"Q9UMS0","fasta_url":"https://rest.uniprot.org/uniprotkb/Q9UMS0.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q9UMS0/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9UMS0"}},"corpus_meta":[{"pmid":"10639125","id":"PMC_10639125","title":"NifS-directed assembly of a transient [2Fe-2S] cluster within the NifU protein.","date":"2000","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/10639125","citation_count":267,"is_preprint":false},{"pmid":"22077971","id":"PMC_22077971","title":"A fatal mitochondrial disease is associated with defective NFU1 function in the maturation of a subset of mitochondrial Fe-S proteins.","date":"2011","source":"American journal of human genetics","url":"https://pubmed.ncbi.nlm.nih.gov/22077971","citation_count":226,"is_preprint":false},{"pmid":"21944046","id":"PMC_21944046","title":"Mutations in iron-sulfur cluster scaffold genes NFU1 and BOLA3 cause a fatal deficiency of multiple respiratory chain and 2-oxoacid dehydrogenase enzymes.","date":"2011","source":"American journal of human genetics","url":"https://pubmed.ncbi.nlm.nih.gov/21944046","citation_count":223,"is_preprint":false},{"pmid":"7947754","id":"PMC_7947754","title":"nifU gene product from Azotobacter vinelandii is a homodimer that contains two identical [2Fe-2S] clusters.","date":"1994","source":"Biochemistry","url":"https://pubmed.ncbi.nlm.nih.gov/7947754","citation_count":130,"is_preprint":false},{"pmid":"16185064","id":"PMC_16185064","title":"NifS-mediated assembly of [4Fe-4S] clusters in the N- and C-terminal domains of the NifU scaffold protein.","date":"2005","source":"Biochemistry","url":"https://pubmed.ncbi.nlm.nih.gov/16185064","citation_count":115,"is_preprint":false},{"pmid":"14993221","id":"PMC_14993221","title":"Iron-sulfur cluster assembly: NifU-directed activation of the nitrogenase Fe protein.","date":"2004","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/14993221","citation_count":111,"is_preprint":false},{"pmid":"27532773","id":"PMC_27532773","title":"Role of Nfu1 and Bol3 in iron-sulfur cluster transfer to mitochondrial clients.","date":"2016","source":"eLife","url":"https://pubmed.ncbi.nlm.nih.gov/27532773","citation_count":107,"is_preprint":false},{"pmid":"10819462","id":"PMC_10819462","title":"Modular organization and identification of a mononuclear iron-binding site within the NifU protein.","date":"2000","source":"Journal of biological inorganic chemistry : JBIC : a publication of the Society of Biological Inorganic Chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/10819462","citation_count":105,"is_preprint":false},{"pmid":"2553733","id":"PMC_2553733","title":"Nitrogen fixation (nif) genes of the cyanobacterium Anabaena species strain PCC 7120. The nifB-fdxN-nifS-nifU operon.","date":"1989","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/2553733","citation_count":101,"is_preprint":false},{"pmid":"11123951","id":"PMC_11123951","title":"Characterization of the NifU and NifS Fe-S cluster formation proteins essential for viability in Helicobacter pylori.","date":"2000","source":"Biochemistry","url":"https://pubmed.ncbi.nlm.nih.gov/11123951","citation_count":97,"is_preprint":false},{"pmid":"1538703","id":"PMC_1538703","title":"The nifU, nifS and nifV gene products are required for activity of all three nitrogenases of Azotobacter vinelandii.","date":"1992","source":"Molecular & general genetics : MGG","url":"https://pubmed.ncbi.nlm.nih.gov/1538703","citation_count":89,"is_preprint":false},{"pmid":"25918518","id":"PMC_25918518","title":"Clinical, biochemical, and genetic spectrum of seven patients with NFU1 deficiency.","date":"2015","source":"Frontiers in genetics","url":"https://pubmed.ncbi.nlm.nih.gov/25918518","citation_count":84,"is_preprint":false},{"pmid":"8875867","id":"PMC_8875867","title":"A modular domain of NifU, a nitrogen fixation cluster protein, is highly conserved in evolution.","date":"1996","source":"Journal of molecular evolution","url":"https://pubmed.ncbi.nlm.nih.gov/8875867","citation_count":52,"is_preprint":false},{"pmid":"17959596","id":"PMC_17959596","title":"Evidence for nifU and nifS participation in the biosynthesis of the iron-molybdenum cofactor of nitrogenase.","date":"2007","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/17959596","citation_count":47,"is_preprint":false},{"pmid":"25477904","id":"PMC_25477904","title":"Cavitating leukoencephalopathy with multiple mitochondrial dysfunction syndrome and NFU1 mutations.","date":"2014","source":"Frontiers in genetics","url":"https://pubmed.ncbi.nlm.nih.gov/25477904","citation_count":46,"is_preprint":false},{"pmid":"27818104","id":"PMC_27818104","title":"Structural/Functional Properties of Human NFU1, an Intermediate [4Fe-4S] Carrier in Human Mitochondrial Iron-Sulfur Cluster Biogenesis.","date":"2016","source":"Structure (London, England : 1993)","url":"https://pubmed.ncbi.nlm.nih.gov/27818104","citation_count":42,"is_preprint":false},{"pmid":"1495390","id":"PMC_1495390","title":"Activator-independent formation of a closed complex between sigma 54-holoenzyme and nifH and nifU promoters of Klebsiella pneumoniae.","date":"1992","source":"Molecular microbiology","url":"https://pubmed.ncbi.nlm.nih.gov/1495390","citation_count":41,"is_preprint":false},{"pmid":"24462778","id":"PMC_24462778","title":"Leukoencephalopathy with cysts and hyperglycinemia may result from NFU1 deficiency.","date":"2014","source":"Mitochondrion","url":"https://pubmed.ncbi.nlm.nih.gov/24462778","citation_count":39,"is_preprint":false},{"pmid":"15667274","id":"PMC_15667274","title":"NifU and NifS are required for the maturation of nitrogenase and cannot replace the function of isc-gene products in Azotobacter vinelandii.","date":"2005","source":"Biochemical Society transactions","url":"https://pubmed.ncbi.nlm.nih.gov/15667274","citation_count":38,"is_preprint":false},{"pmid":"12915448","id":"PMC_12915448","title":"The Lafora disease gene product laforin interacts with HIRIP5, a phylogenetically conserved protein containing a NifU-like domain.","date":"2003","source":"Human molecular genetics","url":"https://pubmed.ncbi.nlm.nih.gov/12915448","citation_count":37,"is_preprint":false},{"pmid":"1880804","id":"PMC_1880804","title":"Organization and function of binding sites for the transcriptional activator NifA in the Klebsiella pneumoniae nifE and nifU promoters.","date":"1991","source":"Journal of molecular biology","url":"https://pubmed.ncbi.nlm.nih.gov/1880804","citation_count":37,"is_preprint":false},{"pmid":"31461310","id":"PMC_31461310","title":"Rats with a Human Mutation of NFU1 Develop Pulmonary Hypertension.","date":"2020","source":"American journal of respiratory cell and molecular biology","url":"https://pubmed.ncbi.nlm.nih.gov/31461310","citation_count":35,"is_preprint":false},{"pmid":"7883714","id":"PMC_7883714","title":"Characterization of nifB, nifS, and nifU genes in the cyanobacterium Anabaena variabilis: NifB is required for the vanadium-dependent nitrogenase.","date":"1995","source":"Journal of bacteriology","url":"https://pubmed.ncbi.nlm.nih.gov/7883714","citation_count":32,"is_preprint":false},{"pmid":"2186362","id":"PMC_2186362","title":"Activation of the Klebsiella pneumoniae nifU promoter: identification of multiple and overlapping upstream NifA binding sites.","date":"1990","source":"Nucleic acids research","url":"https://pubmed.ncbi.nlm.nih.gov/2186362","citation_count":31,"is_preprint":false},{"pmid":"37823603","id":"PMC_37823603","title":"BOLA3 and NFU1 link mitoribosome iron-sulfur cluster assembly to multiple mitochondrial dysfunctions syndrome.","date":"2023","source":"Nucleic acids research","url":"https://pubmed.ncbi.nlm.nih.gov/37823603","citation_count":29,"is_preprint":false},{"pmid":"25758857","id":"PMC_25758857","title":"New spastic paraplegia phenotype associated to mutation of NFU1.","date":"2015","source":"Orphanet journal of rare diseases","url":"https://pubmed.ncbi.nlm.nih.gov/25758857","citation_count":29,"is_preprint":false},{"pmid":"6258035","id":"PMC_6258035","title":"The preparation, efficacy and safety of 'antigenoid' vaccine NFU1 (S-L+) MRC toward prevention of herpes simplex virus infections in human subjects.","date":"1980","source":"Medical microbiology and immunology","url":"https://pubmed.ncbi.nlm.nih.gov/6258035","citation_count":25,"is_preprint":false},{"pmid":"28161430","id":"PMC_28161430","title":"Understanding the Molecular Basis of Multiple Mitochondrial Dysfunctions Syndrome 1 (MMDS1)-Impact of a Disease-Causing Gly208Cys Substitution on Structure and Activity of NFU1 in the Fe/S Cluster Biosynthetic Pathway.","date":"2017","source":"Journal of molecular biology","url":"https://pubmed.ncbi.nlm.nih.gov/28161430","citation_count":23,"is_preprint":false},{"pmid":"32776106","id":"PMC_32776106","title":"Assembly of the [4Fe-4S] cluster of NFU1 requires the coordinated donation of two [2Fe-2S] clusters from the scaffold proteins, ISCU2 and ISCA1.","date":"2020","source":"Human molecular genetics","url":"https://pubmed.ncbi.nlm.nih.gov/32776106","citation_count":20,"is_preprint":false},{"pmid":"33297749","id":"PMC_33297749","title":"Single Mutation in the NFU1 Gene Metabolically Reprograms Pulmonary Artery Smooth Muscle Cells.","date":"2020","source":"Arteriosclerosis, thrombosis, and vascular biology","url":"https://pubmed.ncbi.nlm.nih.gov/33297749","citation_count":19,"is_preprint":false},{"pmid":"36281303","id":"PMC_36281303","title":"In Vitro Demonstration of Human Lipoyl Synthase Catalytic Activity in the Presence of NFU1.","date":"2022","source":"ACS bio & med chem Au","url":"https://pubmed.ncbi.nlm.nih.gov/36281303","citation_count":19,"is_preprint":false},{"pmid":"26688339","id":"PMC_26688339","title":"A leaky splicing mutation in NFU1 is associated with a particular biochemical phenotype. Consequences for the diagnosis.","date":"2015","source":"Mitochondrion","url":"https://pubmed.ncbi.nlm.nih.gov/26688339","citation_count":19,"is_preprint":false},{"pmid":"11342215","id":"PMC_11342215","title":"Identification of human and mouse HIRA-interacting protein-5 (HIRIP5), two mammalian representatives in a family of phylogenetically conserved proteins with a role in the biogenesis of Fe/S proteins.","date":"2001","source":"Biochimica et biophysica acta","url":"https://pubmed.ncbi.nlm.nih.gov/11342215","citation_count":16,"is_preprint":false},{"pmid":"32151725","id":"PMC_32151725","title":"ISCU interacts with NFU1, and ISCU[4Fe-4S] transfers its Fe-S cluster to NFU1 leading to the production of holo-NFU1.","date":"2020","source":"Journal of structural biology","url":"https://pubmed.ncbi.nlm.nih.gov/32151725","citation_count":16,"is_preprint":false},{"pmid":"3053983","id":"PMC_3053983","title":"Further analysis of nitrogen fixation (nif) genes in Azotobacter chroococcum: identification and expression in Klebsiella pneumoniae of nifS, nifV, nifM, and nifB genes and localization of nifE/N-, nifU-, nifA- and fixABC-like genes.","date":"1988","source":"Journal of general microbiology","url":"https://pubmed.ncbi.nlm.nih.gov/3053983","citation_count":15,"is_preprint":false},{"pmid":"32747156","id":"PMC_32747156","title":"A genetic mimic of cerebral palsy: Homozygous NFU1 mutation with marked intrafamilial phenotypic variation.","date":"2020","source":"Brain & development","url":"https://pubmed.ncbi.nlm.nih.gov/32747156","citation_count":14,"is_preprint":false},{"pmid":"29441221","id":"PMC_29441221","title":"NFU1 -Related Disorders as Key Differential Diagnosis of Cavitating Leukoencephalopathy.","date":"2017","source":"Journal of pediatric genetics","url":"https://pubmed.ncbi.nlm.nih.gov/29441221","citation_count":14,"is_preprint":false},{"pmid":"28906594","id":"PMC_28906594","title":"Understanding the molecular basis for multiple mitochondrial dysfunctions syndrome 1 (MMDS1): impact of a disease-causing Gly189Arg substitution on NFU1.","date":"2017","source":"The FEBS journal","url":"https://pubmed.ncbi.nlm.nih.gov/28906594","citation_count":13,"is_preprint":false},{"pmid":"33711344","id":"PMC_33711344","title":"ISCA1 Orchestrates ISCA2 and NFU1 in the Maturation of Human Mitochondrial [4Fe-4S] Proteins.","date":"2021","source":"Journal of molecular biology","url":"https://pubmed.ncbi.nlm.nih.gov/33711344","citation_count":12,"is_preprint":false},{"pmid":"28470589","id":"PMC_28470589","title":"Novel NFU1 Variants Induced MMDS Behaved as Special Leukodystrophy in Chinese Sufferers.","date":"2017","source":"Journal of molecular neuroscience : MN","url":"https://pubmed.ncbi.nlm.nih.gov/28470589","citation_count":10,"is_preprint":false},{"pmid":"3133363","id":"PMC_3133363","title":"Cloning of nifHD from Nostoc commune UTEX 584 and of a flanking region homologous to part of the Azotobacter vinelandii nifU gene.","date":"1988","source":"Journal of bacteriology","url":"https://pubmed.ncbi.nlm.nih.gov/3133363","citation_count":10,"is_preprint":false},{"pmid":"17431550","id":"PMC_17431550","title":"The NMR structure of the domain II of a chloroplastic NifU-like protein OsNifU1A.","date":"2007","source":"Journal of biomolecular NMR","url":"https://pubmed.ncbi.nlm.nih.gov/17431550","citation_count":8,"is_preprint":false},{"pmid":"28906593","id":"PMC_28906593","title":"Analysis of NFU-1 metallocofactor binding-site substitutions-impacts on iron-sulfur cluster coordination and protein structure and function.","date":"2017","source":"The FEBS journal","url":"https://pubmed.ncbi.nlm.nih.gov/28906593","citation_count":8,"is_preprint":false},{"pmid":"6752663","id":"PMC_6752663","title":"The polar effect on nifM of mutations in the nifU,-S,-V genes of Klebsiella pneumoniae depends on their plasmid or chromosomal location.","date":"1982","source":"Molecular & general genetics : MGG","url":"https://pubmed.ncbi.nlm.nih.gov/6752663","citation_count":8,"is_preprint":false},{"pmid":"25953913","id":"PMC_25953913","title":"Involvement of thioredoxin on the scaffold activity of NifU in heterocyst cells of the diazotrophic cyanobacterium Anabaena sp. strain PCC 7120.","date":"2015","source":"Journal of biochemistry","url":"https://pubmed.ncbi.nlm.nih.gov/25953913","citation_count":8,"is_preprint":false},{"pmid":"29326599","id":"PMC_29326599","title":"Nfu1 Mediated ROS Removal Caused by Cd Stress in Tegillarca granosa.","date":"2017","source":"Frontiers in physiology","url":"https://pubmed.ncbi.nlm.nih.gov/29326599","citation_count":5,"is_preprint":false},{"pmid":"31516295","id":"PMC_31516295","title":"\"Idiopathic\" pulmonary arterial hypertension in early infancy: Excluding NFU1 deficiency.","date":"2019","source":"Annals of pediatric cardiology","url":"https://pubmed.ncbi.nlm.nih.gov/31516295","citation_count":5,"is_preprint":false},{"pmid":"27381105","id":"PMC_27381105","title":"NFU1 gene mutation and mitochondrial disorders.","date":"2016","source":"Neurology India","url":"https://pubmed.ncbi.nlm.nih.gov/27381105","citation_count":4,"is_preprint":false},{"pmid":"25606020","id":"PMC_25606020","title":"Mitochondrial Protein Nfu1 Influences Homeostasis of Essential Metals in the Human Fungal Pathogen Cryptococcus neoformans.","date":"2014","source":"Mycobiology","url":"https://pubmed.ncbi.nlm.nih.gov/25606020","citation_count":4,"is_preprint":false},{"pmid":"37211204","id":"PMC_37211204","title":"Structural Plasticity of NFU1 Upon Interaction with Binding Partners: Insights into the Mitochondrial [4Fe-4S] Cluster Pathway.","date":"2023","source":"Journal of molecular biology","url":"https://pubmed.ncbi.nlm.nih.gov/37211204","citation_count":3,"is_preprint":false},{"pmid":"28186588","id":"PMC_28186588","title":"[Analysis of NFU1 gene mutation in a Chinese family affected with multiple mitochondrial dysfunction syndrome].","date":"2017","source":"Zhonghua yi xue yi chuan xue za zhi = Zhonghua yixue yichuanxue zazhi = Chinese journal of medical genetics","url":"https://pubmed.ncbi.nlm.nih.gov/28186588","citation_count":3,"is_preprint":false},{"pmid":"39442618","id":"PMC_39442618","title":"Azotobacter vinelandii scaffold protein NifU transfers iron to NifQ as part of the iron-molybdenum cofactor biosynthesis pathway for nitrogenase.","date":"2024","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/39442618","citation_count":1,"is_preprint":false},{"pmid":"36645076","id":"PMC_36645076","title":"Patient-specific variants of NFU1/NFU-1 disrupt cholinergic signaling in a model of multiple mitochondrial dysfunctions syndrome 1.","date":"2023","source":"Disease models & mechanisms","url":"https://pubmed.ncbi.nlm.nih.gov/36645076","citation_count":1,"is_preprint":false},{"pmid":"41529390","id":"PMC_41529390","title":"The oxygen sensitivity of [4Fe-4S] clusters on the nitrogenase scaffold protein NifU.","date":"2026","source":"Journal of inorganic biochemistry","url":"https://pubmed.ncbi.nlm.nih.gov/41529390","citation_count":1,"is_preprint":false},{"pmid":"17654012","id":"PMC_17654012","title":"Verification and tissue-specific expression of nifU-like gene from the amphioxus Branchiostoma belcheri.","date":"2007","source":"DNA sequence : the journal of DNA sequencing and mapping","url":"https://pubmed.ncbi.nlm.nih.gov/17654012","citation_count":0,"is_preprint":false},{"pmid":"18300158","id":"PMC_18300158","title":"Verification and tissue-specific expression of nifU-like gene from the amphioxus Branchiostoma belcheri.","date":"2008","source":"DNA sequence : the journal of DNA sequencing and mapping","url":"https://pubmed.ncbi.nlm.nih.gov/18300158","citation_count":0,"is_preprint":false},{"pmid":"40233434","id":"PMC_40233434","title":"Yeast models of mutations in NFU1 gene for biochemical characterization and drug screening.","date":"2025","source":"Biochemical and biophysical research communications","url":"https://pubmed.ncbi.nlm.nih.gov/40233434","citation_count":0,"is_preprint":false},{"pmid":null,"id":"bio_10.1101_2025.10.21.683637","title":"<i>Azotobacter vinelandii</i>  glutaredoxin D delivers the core [Fe  <sub>2</sub>  S  <sub>2</sub>  ] cluster to nitrogenase cofactor scaffold protein NifU","date":"2025-10-21","source":"bioRxiv","url":"https://doi.org/10.1101/2025.10.21.683637","citation_count":0,"is_preprint":true},{"pmid":null,"id":"bio_10.1101_2025.02.26.640487","title":"Assessing wheat growth promotion potential of  <i>Delftia lacustris</i>  strain NSC through genomic and physiological characterization","date":"2025-02-27","source":"bioRxiv","url":"https://doi.org/10.1101/2025.02.26.640487","citation_count":0,"is_preprint":true}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":27244,"output_tokens":5546,"usd":0.082461,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":14123,"output_tokens":3928,"usd":0.084407,"stage2_stop_reason":"end_turn"},"total_usd":0.166868,"stage1_batch_id":"msgbatch_013a8chtv3AWyTqv4z4sEF4C","stage2_batch_id":"msgbatch_01AHsuW63vinsvuTgzmQ3n62","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 1994,\n      \"finding\": \"NifU (A. vinelandii) is a homodimer containing one [2Fe-2S]2+/+ cluster per subunit, with complete cysteinyl coordination; the cluster has distinctive spectroscopic properties attributed to a novel arrangement of coordinating cysteine residues.\",\n      \"method\": \"Purification, UV/vis absorption, variable-temperature MCD, EPR, resonance Raman spectroscopy\",\n      \"journal\": \"Biochemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — multiple orthogonal biophysical methods on purified recombinant protein, foundational characterization replicated by subsequent studies\",\n      \"pmids\": [\"7947754\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"NifU (A. vinelandii) interacts with NifS and a transient [2Fe-2S] cluster is assembled on NifU in vitro when incubated with ferric ion, L-cysteine, and catalytic NifS; approximately one transient [2Fe-2S] cluster is assembled per homodimer and is rapidly released upon reduction, consistent with NifU serving as an intermediate Fe-S cluster assembly scaffold.\",\n      \"method\": \"In vitro reconstitution with purified proteins, UV/vis and EPR spectroscopy\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro reconstitution with multiple spectroscopic validations, replicated conceptually in subsequent studies\",\n      \"pmids\": [\"10639125\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"NifU (A. vinelandii) has a modular structure: the N-terminal domain contains a labile rubredoxin-like mononuclear iron-binding site (coordinated by Cys35, Cys62, Cys106) used for Fe-S cluster formation, and the C-terminal domain contains the permanent [2Fe-2S] cluster (coordinated by Cys137, Cys139, Cys172, Cys175); both sites are required for full physiological function.\",\n      \"method\": \"Primary sequence comparison, amino acid substitution/mutagenesis, optical and resonance Raman spectroscopy of recombinant full-length and truncated NifU fragments\",\n      \"journal\": \"Journal of biological inorganic chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — mutagenesis combined with spectroscopic characterization, multiple orthogonal methods\",\n      \"pmids\": [\"10819462\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"Both the N-terminal (IscU-type) and C-terminal (Nfu-type) domains of NifU (A. vinelandii) can independently serve as scaffolds for [4Fe-4S] cluster assembly via NifS, with sequential assembly of [2Fe-2S] then [4Fe-4S] in the N-terminal domain; both domains transfer [4Fe-4S] clusters to apo-nitrogenase Fe protein. A conserved Asp37 in the N-terminal domain plays a critical role in cluster transfer.\",\n      \"method\": \"In vitro NifS-mediated Fe-S cluster assembly on full-length and truncated NifU, UV-vis and Mössbauer spectroscopy, analytical studies, mutagenesis, apo-nitrogenase activation assay\",\n      \"journal\": \"Biochemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — reconstitution, Mössbauer spectroscopy, mutagenesis, and functional transfer assay in one rigorous study\",\n      \"pmids\": [\"16185064\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"Both the N-terminal (IscU-type) and C-terminal (Nfu-type) domains of NifU (A. vinelandii) can separately participate in nitrogenase-specific Fe-S cluster formation in vivo, with the N-terminal domain having the dominant function; this was supported by in vitro cluster assembly and transfer assays activating apo-nitrogenase Fe protein.\",\n      \"method\": \"Amino acid substitution genetics in A. vinelandii, in vitro Fe-S cluster assembly and transfer to apo-nitrogenase Fe protein\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — combined in vivo genetic and in vitro biochemical approaches in single focused study\",\n      \"pmids\": [\"14993221\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"NFU1 functions as a late-acting, substrate-specific maturation factor for a subset of mitochondrial Fe-S proteins: RNAi depletion of NFU1 in human cells markedly decreases lipoic acid synthase (LAS) activity and, consequently, pyruvate dehydrogenase complex (PDHC) activity, and reduces succinate dehydrogenase (complex II) amount, but does not affect other Fe-S proteins tested. In contrast, ISCU depletion severely affects all tested Fe-S proteins. Yeast Nfu1 deletion phenocopies this selective defect (reduced lipoylation and SDH activity).\",\n      \"method\": \"RNAi knockdown in human cells, enzymatic activity assays (LAS, PDHC, SDH), lipoic acid quantification, yeast NFU1 deletion, functional complementation with patient missense mutant protein\",\n      \"journal\": \"American journal of human genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — clean KD in human cells plus yeast KO with orthogonal biochemical readouts, replicated across two organisms\",\n      \"pmids\": [\"22077971\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Mitochondrial isoform of NFU1 (but not cytosolic isoform) is required for proper assembly of Fe-S centers needed for maturation of lipoate-containing 2-oxoacid dehydrogenases and respiratory chain complexes I, II, and III; retroviral transduction of the mitochondrial NFU1 isoform restores both functions in patient fibroblasts.\",\n      \"method\": \"Retroviral vector complementation of patient fibroblasts with isoform-specific NFU1 constructs, measurement of respiratory chain and oxoacid dehydrogenase complex activities\",\n      \"journal\": \"American journal of human genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — isoform-specific complementation rescue with multiple biochemical readouts, single lab\",\n      \"pmids\": [\"21944046\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Human NFU1 protein structure was determined for both N- and C-terminal domains by NMR; SAXS data show full-length apo-NFU1 is monomeric, while two apo-NFU1 subunits coordinate one [4Fe-4S] cluster to form a cluster-linked dimer; holo-NFU1 ([4Fe-4S]-loaded) exists as a trimer of dimers with N-terminal regions forming a tripartite interface. Holo-NFU1 can activate apo-aconitase.\",\n      \"method\": \"NMR spectroscopy, small-angle X-ray scattering (SAXS), size-exclusion chromatography, apo-aconitase activation assay\",\n      \"journal\": \"Structure\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — NMR structure combined with SAXS and functional validation in single rigorous study\",\n      \"pmids\": [\"27818104\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Yeast Nfu1 physically interacts with components of the ISA [4Fe-4S] assembly complex and with client proteins requiring [4Fe-4S] clusters (e.g., lipoic acid synthase, respiratory chain subunits); Nfu1 functions in a late step of [4Fe-4S] cluster biogenesis and its function is of heightened importance during oxidative metabolism. Bol3 (yeast BOLA3 homolog) functions with Nfu1 at this late step to facilitate Fe-S transfer to client proteins.\",\n      \"method\": \"Genetic studies in yeast, proteomic protein-protein interaction studies (physical interaction with ISA complex and client proteins)\",\n      \"journal\": \"eLife\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic epistasis plus proteomic interaction studies, yeast model, multiple orthogonal methods\",\n      \"pmids\": [\"27532773\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"The disease-causing Gly208Cys substitution in NFU1 increases protein dimerization propensity and perturbs secondary structure, which severely impairs the ability of mutant NFU1 to accept an Fe-S cluster from physiologically relevant donor sources, thereby blocking downstream cluster trafficking. The additional cysteine at 208 does not itself serve as a cluster ligand.\",\n      \"method\": \"In vitro protein stability assays, analytical ultracentrifugation/oligomeric state analysis, circular dichroism, Fe-S cluster transfer assays, mutagenesis of cluster-binding site residues\",\n      \"journal\": \"Journal of molecular biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Weak — in vitro mutagenesis and cluster transfer assays, single lab\",\n      \"pmids\": [\"28161430\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"The disease-causing Gly189Arg substitution in NFU1 increases flexibility, decreases stability, and shifts the monomer–dimer equilibrium toward monomer, impairing the protein's ability to receive an Fe-S cluster from physiological donor proteins.\",\n      \"method\": \"In vitro structural analysis, thermal stability assays, analytical ultracentrifugation, Fe-S cluster transfer assays\",\n      \"journal\": \"The FEBS journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Weak — in vitro biochemical and biophysical analysis, single lab\",\n      \"pmids\": [\"28906594\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Mutagenesis of the CXXC cluster-binding motif residues of NFU1 established that the Gly208Cys substitution does not directly coordinate the Fe-S cluster but instead causes global structural alterations that change the oligomerization state and result in MMDS1 disease phenotype.\",\n      \"method\": \"Site-directed mutagenesis of cluster-binding site and Gly208Cys background, spectroscopic cluster coordination analysis, oligomerization assays\",\n      \"journal\": \"The FEBS journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Weak — mutagenesis with spectroscopic readout, single lab study\",\n      \"pmids\": [\"28906593\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Human mitochondrial ISCU2 (ISCU) and ISCA1 are the direct donors of Fe-S clusters to NFU1: ISCU[4Fe-4S] (but not ISCU[2Fe-2S]) transfers its cluster to apo-NFU1 in vitro. NFU1 interacts with both ISCU2 and ISCA1, and the interaction site maps to a conserved hydrophobic patch at the end of the C-terminal alpha-helix of NFU1. Mutagenesis of this interaction site blocks Fe-S cluster acquisition by NFU1 and impairs downstream lipoylation. Ferredoxin 2 aids [4Fe-4S] formation on NFU1.\",\n      \"method\": \"NMR spectroscopy, SAXS, isothermal titration calorimetry (ITC), in vitro Fe-S cluster transfer assays, site-directed mutagenesis, monitoring of downstream client protein abundance\",\n      \"journal\": \"Journal of structural biology / Human molecular genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — two independent studies (PMID 32151725 and PMID 32776106) using reconstitution, NMR/SAXS, ITC, and mutagenesis confirming same interaction and transfer mechanism\",\n      \"pmids\": [\"32151725\", \"32776106\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"ISCA1 is the key mediator of [4Fe-4S] cluster transfer to NFU1: ISCA1 interacts with both ISCA2 and NFU1, but ISCA2 and NFU1 do not interact with each other directly. ISCA1 promotes formation of a transient ISCA1-ISCA2-NFU1 ternary complex, and through its specific interaction with the C-terminal cluster-binding domain of NFU1, drives [4Fe-4S] cluster transfer from the ISCA1-ISCA2 assembly complex to NFU1.\",\n      \"method\": \"NMR spectroscopy-based structural study, protein-protein interaction mapping, [4Fe-4S] cluster transfer assays\",\n      \"journal\": \"Journal of molecular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — NMR structural analysis with functional cluster transfer assays, multiple orthogonal methods in single rigorous study\",\n      \"pmids\": [\"33711344\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Human NFU1 forms a tight complex with human lipoyl synthase (LIAS) in vitro and efficiently restores the auxiliary [4Fe-4S] cluster of LIAS during catalytic turnover, enabling multiple-turnover lipoyl synthesis. BOLA3 has no direct effect on Fe-S cluster transfer from NFU1 or GLRX5 to LIAS. ISCA1 and ISCA2 can also enhance LIAS turnover but only slightly.\",\n      \"method\": \"In vitro complex formation assay, multiple-turnover lipoyl synthase activity assay with purified proteins, comparison with BOLA3, GLRX5, ISCA1, ISCA2\",\n      \"journal\": \"ACS bio & med chem Au\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro reconstitution of complex formation plus functional catalytic assay demonstrating cluster regeneration, single lab with orthogonal methods\",\n      \"pmids\": [\"36281303\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"NFU1 (via the ISCA1-NFU1 node) is required for insertion of the [4Fe-4S] cluster into the mitoribosome assembly factor METTL17; fibroblasts from NFU1-mutant patients show attenuation of mitochondrial protein synthesis, revealing a previously unrecognized role of NFU1 in mitoribosome biogenesis.\",\n      \"method\": \"Silencing of Fe-S cluster biosynthetic/delivery factors, analysis of mitoribosome stability, mitochondrial protein synthesis assays in patient fibroblasts\",\n      \"journal\": \"Nucleic acids research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic silencing plus patient fibroblast biochemical analysis, multiple readouts, single lab\",\n      \"pmids\": [\"37823603\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"Structural plasticity of NFU1 domains is crucial for partner recognition and [4Fe-4S] cluster transfer: SAXS and paramagnetic NMR reveal structural models of ISCA1-ISCA2, ISCA1-ISCA2-NFU1, and ISCA1-NFU1 complexes showing the N-terminal domain of NFU1 acts as a modulator of cluster transfer, and the terminal stable [4Fe-4S]-containing species is the ISCA1-NFU1 complex.\",\n      \"method\": \"SEC-coupled SAXS, paramagnetic NMR, structural modeling of apo and holo complexes\",\n      \"journal\": \"Journal of molecular biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Weak — SAXS and NMR structural data, single lab, no mutagenesis confirmation of N-domain modulator role\",\n      \"pmids\": [\"37211204\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"HIRIP5 (human NFU1/CGI-33) interacts specifically with the Lafora disease protein laforin both in vitro and in vivo; laforin uses its N-terminal CBD-4 domain to interact with the C-terminal NifU-like domain of HIRIP5/NFU1. Laforin dephosphorylates HIRIP5 in vitro, identifying NFU1 as a laforin substrate.\",\n      \"method\": \"Yeast two-hybrid screen, in vitro and in vivo co-immunoprecipitation, in vitro phosphatase assay\",\n      \"journal\": \"Human molecular genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal in vitro and in vivo interaction assays plus in vitro phosphatase activity, single lab\",\n      \"pmids\": [\"12915448\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"Human HIRIP5 (NFU1) interacts with the HIRA protein in yeast two-hybrid and in vitro protein interaction experiments; HIRIP5/NFU1 is implicated in iron metabolism in mitochondria based on homology to yeast NFU1.\",\n      \"method\": \"Yeast two-hybrid screen, in vitro protein interaction assay\",\n      \"journal\": \"Biochimica et biophysica acta\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single yeast two-hybrid and in vitro pulldown, no functional mechanistic follow-up for the HIRA interaction\",\n      \"pmids\": [\"11342215\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"C. elegans patient-specific nfu-1 variants (Gly147Arg and Gly166Cys, orthologs of human MMDS1 mutations) cause allele-specific dysfunction of acetylcholine signaling at neuromuscular junctions: Gly147Arg causes hypersensitivity to acetylcholine rescued by knockdown of acetylcholine release, while Gly166Cys causes predominantly postsynaptic acetylcholine hypersensitivity.\",\n      \"method\": \"C. elegans patient-variant knock-in strains, acetylcholine sensitivity assays, RNAi knockdown rescue\",\n      \"journal\": \"Disease models & mechanisms\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — defined cellular/synaptic phenotype with genetic rescue in a model organism, single lab\",\n      \"pmids\": [\"36645076\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Rats carrying the human NFU1 G206C mutation (equivalent to human G208C, introduced by CRISPR/Cas9) show decreased expression and activity of mitochondrial Complex II, markedly decreased pyruvate dehydrogenase activity, and decreased lipoate binding, confirming NFU1's role in Fe-S cluster delivery to Complex II and lipoic acid synthase in vivo. Male sex partially compensates via increased ISCU expression and complex IV activity.\",\n      \"method\": \"CRISPR/Cas9 knock-in rat model, mitochondrial complex activity assays, pyruvate dehydrogenase activity, lipoate binding analysis, protein expression studies\",\n      \"journal\": \"American journal of respiratory cell and molecular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo humanized knock-in model with multiple biochemical readouts confirming mechanism from cell culture studies\",\n      \"pmids\": [\"31461310\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"Human NFU1 is a mitochondrial late-acting [4Fe-4S] cluster carrier protein that receives its [4Fe-4S] cluster from ISCU2 (which transfers the cluster as ISCU[4Fe-4S]) and from the ISCA1-ISCA2 complex via a transient ISCA1-ISCA2-NFU1 ternary complex orchestrated by ISCA1, then delivers the cluster to a specific subset of mitochondrial client proteins—most notably lipoic acid synthase (LIAS), succinate dehydrogenase (complex II), and the METTL17 mitoribosome assembly factor—thereby supporting lipoylation of pyruvate dehydrogenase, α-ketoglutarate dehydrogenase, and the glycine cleavage system, as well as respiratory chain assembly; loss-of-function mutations cause Multiple Mitochondrial Dysfunctions Syndrome 1 (MMDS1) characterized by combined defects in lipoic acid-dependent enzymes and respiratory chain complexes.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"NFU1 is a late-acting mitochondrial [4Fe-4S] cluster carrier that delivers clusters to a defined subset of client proteins, supporting lipoic acid-dependent metabolism and respiratory chain assembly [#5, #6]. The protein is modular, built from an N-terminal IscU-type domain and a C-terminal Nfu-type cluster-binding domain, a architecture first defined in the bacterial ortholog NifU where the two domains independently serve as scaffolds for sequential [2Fe-2S]/[4Fe-4S] assembly and cluster transfer [#0, #2, #3]; human apo-NFU1 is monomeric, coordinates one [4Fe-4S] cluster across two subunits as a cluster-linked dimer, and assembles into a holo trimer-of-dimers competent to activate apo-aconitase [#7]. NFU1 receives its cluster from upstream donors: ISCU2 in its [4Fe-4S] form transfers cluster to apo-NFU1, with ferredoxin 2 aiding cluster formation, and the interaction maps to a conserved hydrophobic patch on the NFU1 C-terminal helix [#12]. ISCA1 orchestrates an alternative route, bridging ISCA2 and NFU1 in a transient ISCA1-ISCA2-NFU1 ternary complex that resolves to a stable [4Fe-4S]-loaded ISCA1-NFU1 species [#13, #16]. NFU1 then matures specific clients: it forms a tight complex with lipoyl synthase (LIAS) and regenerates the auxiliary [4Fe-4S] cluster consumed during lipoyl synthesis, enabling multiple-turnover catalysis [#14], and the ISCA1-NFU1 node inserts the [4Fe-4S] cluster into the mitoribosome assembly factor METTL17 [#15]. Loss of NFU1 selectively impairs lipoylation of 2-oxoacid dehydrogenases (pyruvate dehydrogenase, α-ketoglutarate dehydrogenase) and reduces succinate dehydrogenase/complex II and other respiratory chain activities without globally affecting all Fe-S proteins [#5, #6, #20]. Disease-causing missense mutations (e.g., Gly208Cys, Gly189Arg) destabilize the protein and shift its monomer-dimer equilibrium, blocking cluster acquisition from physiological donors rather than acting through direct cluster ligation, causing Multiple Mitochondrial Dysfunctions Syndrome 1 [#9, #10, #11, #20].\",\n  \"teleology\": [\n    {\n      \"year\": 1994,\n      \"claim\": \"Establishing that the NifU scaffold carries a spectroscopically distinct cysteine-coordinated Fe-S cluster defined the founding biochemical identity of the NFU protein family.\",\n      \"evidence\": \"Biophysical characterization (UV/vis, MCD, EPR, resonance Raman) of purified A. vinelandii NifU homodimer\",\n      \"pmids\": [\"7947754\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Bacterial ortholog only\", \"Did not define the modular domain organization\", \"No connection to human mitochondrial clients\"]\n    },\n    {\n      \"year\": 2000,\n      \"claim\": \"Reconstitution showed NifU acts as a transient Fe-S assembly scaffold downstream of the cysteine desulfurase, framing the family as cluster intermediates rather than terminal cofactor proteins.\",\n      \"evidence\": \"In vitro reconstitution of NifU with NifS, ferric ion and L-cysteine, monitored by UV/vis and EPR\",\n      \"pmids\": [\"10639125\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Bacterial system\", \"Did not identify downstream cluster acceptors\", \"Mechanism of release inferred from reduction sensitivity\"]\n    },\n    {\n      \"year\": 2000,\n      \"claim\": \"Mapping NifU's two cluster-binding sites to distinct N- and C-terminal domains established the bilobed architecture later recapitulated in human NFU1.\",\n      \"evidence\": \"Sequence comparison, mutagenesis of coordinating cysteines, and Raman/optical spectroscopy of NifU fragments\",\n      \"pmids\": [\"10819462\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Functional division of labor between domains not resolved\", \"Bacterial protein\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Demonstrating both NifU domains assemble and transfer [4Fe-4S] clusters to apo-nitrogenase clarified that the family delivers higher-order clusters, not just [2Fe-2S], and identified a conserved Asp critical for transfer.\",\n      \"evidence\": \"In vitro NifS-mediated assembly, Mössbauer spectroscopy, mutagenesis, apo-nitrogenase activation assays (with in vivo genetic support from prior work)\",\n      \"pmids\": [\"16185064\", \"14993221\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Nitrogenase-specific clients in bacteria\", \"Does not address mitochondrial client specificity\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Defining NFU1 as a substrate-specific late-acting maturation factor explained why its loss produces a selective biochemical signature—lipoylation and complex II defects—rather than the global Fe-S failure seen with ISCU.\",\n      \"evidence\": \"RNAi in human cells and yeast deletion with LAS/PDHC/SDH activity and lipoate assays, plus isoform-specific retroviral complementation of patient fibroblasts\",\n      \"pmids\": [\"22077971\", \"21944046\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct cluster donors and acceptors not yet biochemically identified\", \"Mechanism of client selectivity unknown\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Structural determination of human NFU1 resolved its oligomeric states and showed holo-NFU1 is competent to activate an apo Fe-S enzyme, providing a structural basis for cluster carriage.\",\n      \"evidence\": \"NMR domain structures, SAXS oligomeric analysis, SEC, and apo-aconitase activation assay; plus yeast genetic/proteomic interactions with the ISA complex and BOLA3 homolog Bol3\",\n      \"pmids\": [\"27818104\", \"27532773\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Donor-to-NFU1 transfer mechanism not yet mapped at residue level\", \"BOLA3/Bol3 functional contribution inferred genetically\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Biophysical dissection of MMDS1 mutations established that pathogenicity arises from destabilization and altered oligomerization that block cluster acceptance, not from disrupted cluster ligation.\",\n      \"evidence\": \"In vitro stability, analytical ultracentrifugation, CD, and Fe-S transfer assays on Gly208Cys and Gly189Arg variants with cluster-site mutagenesis\",\n      \"pmids\": [\"28161430\", \"28906594\", \"28906593\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single-lab in vitro work\", \"Donor identity not defined in these studies\", \"In vivo consequences inferred\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Identifying ISCU2 and ISCA1 as direct cluster donors and mapping the interaction interface defined the upstream half of the NFU1 trafficking pathway.\",\n      \"evidence\": \"NMR, SAXS, ITC, in vitro [4Fe-4S] transfer assays, mutagenesis of the C-terminal hydrophobic patch, with ferredoxin 2 supporting cluster formation; plus humanized G206C knock-in rat confirming complex II/PDH/lipoate defects in vivo\",\n      \"pmids\": [\"32151725\", \"32776106\", \"31461310\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Relative in vivo contribution of ISCU2 vs ISCA1 routes unresolved\", \"Sex-dependent compensation mechanism only partially explained\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Showing ISCA1 bridges ISCA2 and NFU1 in a transient ternary complex established the molecular choreography of cluster handoff to NFU1.\",\n      \"evidence\": \"NMR structural study, interaction mapping, and [4Fe-4S] transfer assays of ISCA1/ISCA2/NFU1\",\n      \"pmids\": [\"33711344\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Kinetics of ternary complex resolution not quantified\", \"Structural models lack high-resolution validation\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Direct LIAS complex formation/cluster regeneration and METTL17 cluster insertion defined NFU1's terminal client-delivery functions, expanding its role to mitoribosome biogenesis.\",\n      \"evidence\": \"In vitro LIAS multiple-turnover lipoyl synthesis assay; silencing and patient-fibroblast mitochondrial translation/mitoribosome stability assays; plus SAXS/paramagnetic NMR models defining the stable ISCA1-NFU1 endpoint\",\n      \"pmids\": [\"36281303\", \"37823603\", \"37211204\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"N-domain modulator role lacks mutagenesis confirmation\", \"BOLA3 found dispensable for LIAS transfer, contrasting earlier genetic data\", \"METTL17 study single lab\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How NFU1 achieves client selectivity—distinguishing LIAS, complex II, and METTL17 from other Fe-S apoproteins—remains mechanistically undefined.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No structural model of an NFU1-client transfer complex\", \"Determinants of client discrimination unknown\", \"Role of accessory factors in selectivity unresolved\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140104\", \"supporting_discovery_ids\": [5, 12, 14]},\n      {\"term_id\": \"GO:0051536\", \"supporting_discovery_ids\": [7, 12]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005739\", \"supporting_discovery_ids\": [5, 6]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-1430728\", \"supporting_discovery_ids\": [5, 6, 20]},\n      {\"term_id\": \"R-HSA-1852241\", \"supporting_discovery_ids\": [15]}\n    ],\n    \"complexes\": [\n      \"ISCA1-ISCA2-NFU1 ternary complex\",\n      \"ISCA1-NFU1 complex\",\n      \"NFU1-LIAS complex\"\n    ],\n    \"partners\": [\n      \"ISCU\",\n      \"ISCA1\",\n      \"ISCA2\",\n      \"LIAS\",\n      \"METTL17\",\n      \"BOLA3\",\n      \"FDX2\",\n      \"HIRA\"\n    ],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":7,"faith_total":7,"faith_pct":100.0}}