{"gene":"BOLA3","run_date":"2026-04-28T17:12:38","timeline":{"discoveries":[{"year":2011,"finding":"BOLA3 is required for the biogenesis of iron-sulfur ([Fe-S]) clusters necessary for normal maturation of lipoate-containing 2-oxoacid dehydrogenases and assembly of mitochondrial respiratory chain complexes I, II, and III. Retroviral transduction with the mitochondrial isoform 1 (but not isoform 2) of BOLA3 rescued both respiratory chain function and oxoacid dehydrogenase activity in patient fibroblasts.","method":"Retroviral complementation of patient fibroblasts with isoform-specific BOLA3 constructs; biochemical enzyme activity assays","journal":"American journal of human genetics","confidence":"High","confidence_rationale":"Tier 2 — reciprocal isoform rescue experiment with defined biochemical phenotype, replicated by subsequent independent labs","pmids":["21944046"],"is_preprint":false},{"year":2012,"finding":"A homozygous missense mutation in BOLA3 causes combined deficiency of respiratory chain complexes I, II, and II+III and pyruvate dehydrogenase complex; lentiviral expression of wild-type mitochondrial BOLA3 isoform in patient fibroblasts restored residual enzyme activities and lipoic acid levels, confirming BOLA3's role in Fe-S cluster biogenesis and lipoylation.","method":"Exome sequencing; lentiviral complementation; biochemical enzyme activity assays; lipoic acid quantification","journal":"Journal of inherited metabolic disease","confidence":"High","confidence_rationale":"Tier 2 — independent replication of functional rescue with multiple biochemical readouts","pmids":["22562699"],"is_preprint":false},{"year":2013,"finding":"BOLA3 mutations cause deficiency of lipoylation of mitochondrial proteins and deficient glycine cleavage enzyme activity, impacting lipoate-dependent enzymes including pyruvate dehydrogenase; transfection with native BOLA3 corrected the biochemical deficiency, demonstrating its essential role in lipoate biosynthesis.","method":"Genetic sequencing; cell transfection complementation; lipoylation assay; enzyme activity measurement","journal":"Brain : a journal of neurology","confidence":"High","confidence_rationale":"Tier 2 — complementation rescue with multiple enzyme readouts, independent cohort","pmids":["24334290"],"is_preprint":false},{"year":2017,"finding":"Human mitochondrial BOLA3 forms a [2Fe-2S] cluster-bridged dimeric heterocomplex with the monothiol glutaredoxin GRX5. The BOLA3-GRX5 complex coordinates an oxidized, ferredoxin-like [2Fe-2S]2+ cluster, in contrast to the reduced Rieske-type [2Fe-2S]1+ cluster found in the BOLA1-GRX5 complex. The BOLA1-GRX5 complex has higher cluster binding affinity than BOLA3-GRX5.","method":"UV/vis, CD, EPR, NMR spectroscopy; computational protein-protein docking; in vitro reconstitution of complexes","journal":"Biochimica et biophysica acta. General subjects","confidence":"High","confidence_rationale":"Tier 1 — multiple orthogonal biophysical and spectroscopic methods with in vitro reconstitution","pmids":["28483642"],"is_preprint":false},{"year":2018,"finding":"The [2Fe-2S] cluster-bridged BOLA3-GLRX5 heterocomplex functions as a cluster trafficking intermediate: apo BOLA3-glutaredoxin complexes accept [2Fe-2S] clusters from donors (ISCU and [2Fe-2S](GS)4), preferentially forming the heterodimer over the holo glutaredoxin homodimer; holo BOLA3-GLRX5 transfers clusters to apo acceptors at rates comparable to other Fe-S trafficking proteins. ITC confirmed strong binding of apo BOLA3 with GLRX5 and weak binding with NFU1.","method":"In vitro cluster transfer assays; isothermal titration calorimetry (ITC); UV/vis spectroscopy","journal":"Metallomics : integrated biometal science","confidence":"High","confidence_rationale":"Tier 1 — reconstituted in vitro cluster exchange with quantitative binding data and kinetics","pmids":["30137089"],"is_preprint":false},{"year":2019,"finding":"Human BOLA3 can form a functional [2Fe-2S]-bridged homodimer capable of Fe-S cluster binding and inter-protein cluster transfer, in addition to its known heterodimeric interactions with GLRX5 and NFU1.","method":"In vitro reconstitution; spectroscopic characterization; cluster transfer assays","journal":"Journal of biological inorganic chemistry : JBIC","confidence":"Medium","confidence_rationale":"Tier 1 — in vitro reconstitution, single lab","pmids":["31486956"],"is_preprint":false},{"year":2021,"finding":"The disease-causing Ile67Asn substitution in BOLA3 impairs the ability of BOLA3 to bind its physiological partner GLRX5 and prevents formation of the [2Fe-2S]-bridged heterocomplex, thereby blocking downstream cluster reconstitution, without causing major overall structural changes to BOLA3 itself.","method":"1H-15N HSQC NMR; ion mobility native mass spectrometry; in vitro cluster reconstitution assays","journal":"Metallomics : integrated biometal science","confidence":"High","confidence_rationale":"Tier 1 — multiple orthogonal methods (NMR, native MS, cluster assays) with disease-relevant mutagenesis","pmids":["33693876"],"is_preprint":false},{"year":2021,"finding":"The Cys59Tyr BOLA3 mutation structurally perturbs the [2Fe-2S] cluster-binding region of BOLA3 without abolishing cluster binding on the BOLA3-GLRX5 heterocomplex; Tyr59 does not replace Cys59 as a cluster ligand, but promotes formation of an aberrant apo BOLA3-GLRX5 complex, explaining the unique milder clinical phenotype.","method":"NMR; UV/vis, CD, EPR spectroscopy; experimentally driven molecular docking; size exclusion chromatography","journal":"International journal of molecular sciences","confidence":"High","confidence_rationale":"Tier 1 — multiple orthogonal spectroscopic and structural methods with mechanistic mutagenesis validation","pmids":["34063696"],"is_preprint":false},{"year":2021,"finding":"BOLA3 deficiency in beige adipocytes inhibits thermogenesis by impairing mitochondrial homeostasis (reduced respiratory chain complexes and mitochondrial formation) and adrenergic signaling-induced lipolysis, without affecting lipogenesis.","method":"Lentiviral shRNA knockdown in differentiated beige adipocytes; Seahorse respirometry; Western blot for respiratory chain complexes; lipolysis assay","journal":"Frontiers in endocrinology","confidence":"Medium","confidence_rationale":"Tier 2 — clean KD with defined cellular phenotypes, single lab","pmids":["33505355"],"is_preprint":false},{"year":2023,"finding":"The His96Arg BOLA3 mutation does not impair BOLA3-GLRX5 interaction but leads to an aberrant [2Fe-2S]-BOLA3-GLRX5 heterocomplex that cannot assemble a [4Fe-4S] cluster on NFU1, establishing that His96 is a critical [2Fe-2S] cluster ligand in the BOLA3-GLRX5 complex and that [4Fe-4S] delivery to NFU1 is downstream of the BOLA3-GLRX5 node.","method":"Size exclusion chromatography; NMR; UV/vis; CD; EPR spectroscopy; in vitro [4Fe-4S] cluster assembly assay on NFU1","journal":"International journal of molecular sciences","confidence":"High","confidence_rationale":"Tier 1 — multiple orthogonal methods, disease mutation used to establish mechanistic pathway step","pmids":["37511493"],"is_preprint":false},{"year":2023,"finding":"The mitoribosome receives its [2Fe-2S] clusters from the GLRX5-BOLA3 node; loss of BOLA3 attenuates mitochondrial protein synthesis through impaired [2Fe-2S] cluster assembly into the mitoribosome small subunit. One of the mitoribosomal [2Fe-2S] clusters senses changes in the redox environment, providing a regulatory mechanism for organellar protein synthesis.","method":"siRNA silencing of Fe-S cluster biosynthetic factors; mitoribosome stability assays; mitochondrial protein synthesis assays in BOLA3-mutant patient fibroblasts; structure-function correlation studies","journal":"Nucleic acids research","confidence":"High","confidence_rationale":"Tier 2 — multiple complementary experiments in human patient fibroblasts and siRNA knockdowns with defined mechanistic readouts","pmids":["37823603"],"is_preprint":false},{"year":2025,"finding":"Metabolomic analysis of BOLA3-deficient patient fibroblasts shows elevated lactic acid, pyruvic acid, TCA cycle intermediates (α-ketoglutaric acid, succinic acid), branched-chain amino acids, and lysine/tryptophan metabolites, with near-absent complex I and II bands; aconitase activity is unaffected. This defines BOLA3 as specifically involved in [4Fe-4S] cluster delivery to respiratory chain complexes I and II and lipoic acid synthetase, but not aconitase.","method":"Capillary electrophoresis time-of-flight mass spectrometry metabolomics; BN-PAGE/Western blot; in-gel enzyme staining of mitochondrial complexes in patient fibroblasts","journal":"Molecular genetics and metabolism","confidence":"Medium","confidence_rationale":"Tier 2 — multi-method biochemical analysis in patient cells defining pathway specificity, single lab","pmids":["40273865"],"is_preprint":false}],"current_model":"BOLA3 is a mitochondrial protein that forms a [2Fe-2S] cluster-bridged heterocomplex with the monothiol glutaredoxin GLRX5 (coordinating an oxidized ferredoxin-like [2Fe-2S]2+ cluster), which serves as an intermediate node for trafficking [2Fe-2S] clusters to the mitoribosome and for assembling [4Fe-4S] clusters on NFU1, thereby enabling maturation of respiratory chain complexes I and II, lipoic acid synthetase (and thus lipoate-dependent 2-oxoacid dehydrogenases), and mitoribosomal subunits; loss of BOLA3 function simultaneously impairs mitochondrial protein synthesis, respiratory chain activity, and lipoylation-dependent enzyme activities."},"narrative":{"teleology":[{"year":2011,"claim":"Establishing that BOLA3 is essential for Fe-S cluster-dependent maturation of respiratory chain complexes and lipoate-containing enzymes resolved the genetic basis of a combined mitochondrial dysfunction syndrome and identified a new Fe-S biogenesis factor.","evidence":"Retroviral complementation of BOLA3-mutant patient fibroblasts with isoform-specific constructs; biochemical enzyme assays","pmids":["21944046"],"confidence":"High","gaps":["Molecular mechanism of BOLA3 action unknown","Direct protein partners unidentified","Whether BOLA3 acts at [2Fe-2S] or [4Fe-4S] stage undetermined"]},{"year":2012,"claim":"Independent replication confirmed BOLA3 loss causes combined respiratory chain and lipoylation deficiency, and demonstrated that wild-type BOLA3 restores lipoic acid levels, cementing the link between Fe-S biogenesis and lipoate biosynthesis.","evidence":"Exome sequencing of new patients; lentiviral complementation; lipoic acid quantification in patient fibroblasts","pmids":["22562699","24334290"],"confidence":"High","gaps":["Physical interaction partners not identified","Whether glycine cleavage system impairment is direct or indirect through lipoylation unclear"]},{"year":2017,"claim":"Biophysical reconstitution of the BOLA3-GLRX5 [2Fe-2S]-bridged heterocomplex defined the molecular species through which BOLA3 acts, revealing it coordinates an oxidized ferredoxin-like [2Fe-2S]²⁺ cluster distinct from the BOLA1-GLRX5 complex.","evidence":"UV/vis, CD, EPR, NMR spectroscopy and computational docking of purified human proteins","pmids":["28483642"],"confidence":"High","gaps":["Direction of cluster flow (donor vs. acceptor) not yet demonstrated","In vivo relevance of heterocomplex not confirmed"]},{"year":2018,"claim":"Quantitative in vitro cluster transfer experiments established that the BOLA3-GLRX5 heterocomplex functions as a bona fide trafficking intermediate, accepting [2Fe-2S] clusters from ISCU and transferring them to downstream acceptors, and revealed weak binding of apo BOLA3 to NFU1.","evidence":"In vitro cluster transfer kinetics; isothermal titration calorimetry; UV/vis spectroscopy","pmids":["30137089"],"confidence":"High","gaps":["Whether BOLA3-GLRX5 directly provides clusters to NFU1 for [4Fe-4S] assembly not shown","BOLA3 homodimer physiological relevance unclear"]},{"year":2021,"claim":"Structural and biochemical analysis of disease-causing mutations (Ile67Asn, Cys59Tyr) revealed that pathogenicity operates through distinct mechanisms — loss of GLRX5 binding versus perturbation of the cluster-binding site — explaining genotype-phenotype variability.","evidence":"NMR, native MS, EPR spectroscopy, and in vitro cluster reconstitution with mutant BOLA3 proteins","pmids":["33693876","34063696"],"confidence":"High","gaps":["In vivo validation of mutant complex formation not performed","Whether aberrant apo complex has gain-of-function effects unknown"]},{"year":2023,"claim":"The His96Arg mutation demonstrated that His96 is a critical [2Fe-2S] cluster ligand in the heterocomplex and that [4Fe-4S] cluster assembly on NFU1 lies directly downstream of the BOLA3-GLRX5 node, ordering the pathway from [2Fe-2S] trafficking to [4Fe-4S] maturation.","evidence":"Size exclusion chromatography, NMR, EPR, CD spectroscopy, and in vitro [4Fe-4S] cluster assembly assay on NFU1","pmids":["37511493"],"confidence":"High","gaps":["Complete set of cluster ligands in the heterocomplex not fully resolved","Whether BOLA3-GLRX5 directly donates to NFU1 or requires additional intermediates in vivo unknown"]},{"year":2023,"claim":"Discovery that the mitoribosome receives [2Fe-2S] clusters from the GLRX5-BOLA3 node expanded BOLA3 function beyond respiratory chain and lipoylation to mitochondrial translation, and revealed redox-sensing by a mitoribosomal [2Fe-2S] cluster as a regulatory mechanism.","evidence":"siRNA knockdown of Fe-S factors; mitoribosome stability and translation assays in BOLA3-mutant patient fibroblasts","pmids":["37823603"],"confidence":"High","gaps":["Identity of the mitoribosomal [2Fe-2S] acceptor protein not specified","Whether translation defect contributes to respiratory chain loss or is independent phenotype unclear"]},{"year":2025,"claim":"Metabolomic profiling of BOLA3-deficient cells defined pathway specificity: BOLA3 is required for [4Fe-4S] delivery to complexes I, II, and lipoic acid synthetase but not for aconitase maturation, distinguishing BOLA3 from other late-acting Fe-S factors.","evidence":"CE-TOF-MS metabolomics, BN-PAGE, and in-gel enzyme activity in patient fibroblasts","pmids":["40273865"],"confidence":"Medium","gaps":["Mechanism by which aconitase escapes BOLA3 dependence not explained","Single-lab metabolomic study without independent replication"]},{"year":null,"claim":"The structural basis of the intact [2Fe-2S]-BOLA3-GLRX5 heterocomplex, the mechanism by which it selectively delivers clusters to NFU1 versus the mitoribosome, and whether the BOLA3 homodimer has a physiological role remain unresolved.","evidence":"","pmids":[],"confidence":"Low","gaps":["No high-resolution structure of the holo BOLA3-GLRX5 heterocomplex","Selectivity mechanism for [2Fe-2S] delivery to mitoribosome vs. NFU1 unknown","Physiological relevance of BOLA3 homodimer not established in vivo"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140104","term_label":"molecular carrier activity","supporting_discovery_ids":[3,4,9,10]}],"localization":[{"term_id":"GO:0005739","term_label":"mitochondrion","supporting_discovery_ids":[0,1,2,3,10]}],"pathway":[{"term_id":"R-HSA-1430728","term_label":"Metabolism","supporting_discovery_ids":[0,1,2,4,9,11]},{"term_id":"R-HSA-1643685","term_label":"Disease","supporting_discovery_ids":[0,1,6,7]}],"complexes":["BOLA3-GLRX5 [2Fe-2S]-bridged heterocomplex"],"partners":["GLRX5","NFU1","ISCU"],"other_free_text":[]},"mechanistic_narrative":"BOLA3 is a mitochondrial iron-sulfur (Fe-S) cluster trafficking factor that bridges Fe-S cluster biogenesis to the maturation of respiratory chain complexes, lipoic acid-dependent enzymes, and the mitoribosome. BOLA3 forms a [2Fe-2S] cluster-bridged heterocomplex with the monothiol glutaredoxin GLRX5, which accepts clusters from upstream donors (ISCU) and delivers them downstream to NFU1 for [4Fe-4S] cluster assembly on respiratory chain complexes I and II and lipoic acid synthetase, as well as directly to the mitoribosome small subunit for mitochondrial protein synthesis [PMID:28483642, PMID:30137089, PMID:37511493, PMID:37823603]. Disease-causing mutations in BOLA3 (e.g., Ile67Asn, His96Arg) disrupt either GLRX5 binding or cluster coordination within the heterocomplex, abolishing downstream [4Fe-4S] assembly on NFU1 and causing combined deficiency of respiratory chain complexes I, II, and III, pyruvate dehydrogenase, glycine cleavage enzyme, and lipoylation, while sparing aconitase [PMID:33693876, PMID:37511493, PMID:40273865]. Biallelic loss-of-function mutations in BOLA3 cause multiple mitochondrial dysfunctions syndrome type 2 (MMDS2), a severe disorder characterized by combined respiratory chain and lipoylation defects [PMID:21944046, PMID:22562699, PMID:24334290]."},"prefetch_data":{"uniprot":{"accession":"Q53S33","full_name":"BolA-like protein 3","aliases":[],"length_aa":107,"mass_kda":12.1,"function":"Acts as a mitochondrial iron-sulfur (Fe-S) cluster assembly factor that facilitates (Fe-S) cluster insertion into a subset of mitochondrial proteins. Probably acts together with NFU1 (PubMed:27532772)","subcellular_location":"Mitochondrion","url":"https://www.uniprot.org/uniprotkb/Q53S33/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/BOLA3","classification":"Not Classified","n_dependent_lines":129,"n_total_lines":1208,"dependency_fraction":0.10678807947019868},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/BOLA3","total_profiled":1310},"omim":[{"mim_id":"619219","title":"CHROMOSOME 2 OPEN READING FRAME 69; C2ORF69","url":"https://www.omim.org/entry/619219"},{"mim_id":"616859","title":"SPASTICITY, CHILDHOOD-ONSET, WITH HYPERGLYCINEMIA; SPAHGC","url":"https://www.omim.org/entry/616859"},{"mim_id":"614462","title":"HYPERGLYCINEMIA, LACTIC ACIDOSIS, AND SEIZURES; HGCLAS","url":"https://www.omim.org/entry/614462"},{"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":"Nuclear bodies","reliability":"Supported"},{"location":"Mitochondria","reliability":"Supported"},{"location":"Cytosol","reliability":"Additional"}],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in all","driving_tissues":[{"tissue":"tongue","ntpm":162.0}],"url":"https://www.proteinatlas.org/search/BOLA3"},"hgnc":{"alias_symbol":[],"prev_symbol":[]},"alphafold":{"accession":"Q53S33","domains":[{"cath_id":"3.30.300.90","chopping":"30-102","consensus_level":"high","plddt":88.6485,"start":30,"end":102}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q53S33","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q53S33-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q53S33-F1-predicted_aligned_error_v6.png","plddt_mean":80.94},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=BOLA3","jax_strain_url":"https://www.jax.org/strain/search?query=BOLA3"},"sequence":{"accession":"Q53S33","fasta_url":"https://rest.uniprot.org/uniprotkb/Q53S33.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q53S33/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q53S33"}},"corpus_meta":[{"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":220,"is_preprint":false},{"pmid":"24334290","id":"PMC_24334290","title":"Variant non ketotic hyperglycinemia is caused by mutations in LIAS, BOLA3 and the novel gene GLRX5.","date":"2013","source":"Brain : a journal of neurology","url":"https://pubmed.ncbi.nlm.nih.gov/24334290","citation_count":170,"is_preprint":false},{"pmid":"22562699","id":"PMC_22562699","title":"Homozygous missense mutation in BOLA3 causes multiple mitochondrial dysfunctions syndrome in two siblings.","date":"2012","source":"Journal of inherited metabolic disease","url":"https://pubmed.ncbi.nlm.nih.gov/22562699","citation_count":75,"is_preprint":false},{"pmid":"28483642","id":"PMC_28483642","title":"Structural insights into the molecular function of human [2Fe-2S] BOLA1-GRX5 and [2Fe-2S] BOLA3-GRX5 complexes.","date":"2017","source":"Biochimica et biophysica acta. General subjects","url":"https://pubmed.ncbi.nlm.nih.gov/28483642","citation_count":44,"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":26,"is_preprint":false},{"pmid":"30137089","id":"PMC_30137089","title":"Cluster exchange reactivity of [2Fe-2S] cluster-bridged complexes of BOLA3 with monothiol glutaredoxins.","date":"2018","source":"Metallomics : integrated biometal science","url":"https://pubmed.ncbi.nlm.nih.gov/30137089","citation_count":20,"is_preprint":false},{"pmid":"29501406","id":"PMC_29501406","title":"An infant case of diffuse cerebrospinal lesions and cardiomyopathy caused by a BOLA3 mutation.","date":"2018","source":"Brain & development","url":"https://pubmed.ncbi.nlm.nih.gov/29501406","citation_count":19,"is_preprint":false},{"pmid":"30302924","id":"PMC_30302924","title":"Imaging phenotype of multiple mitochondrial dysfunction syndrome 2, a rare BOLA3-associated leukodystrophy.","date":"2018","source":"American journal of medical genetics. Part A","url":"https://pubmed.ncbi.nlm.nih.gov/30302924","citation_count":13,"is_preprint":false},{"pmid":"33505355","id":"PMC_33505355","title":"Bola3 Regulates Beige Adipocyte Thermogenesis via Maintaining Mitochondrial Homeostasis and Lipolysis.","date":"2021","source":"Frontiers in endocrinology","url":"https://pubmed.ncbi.nlm.nih.gov/33505355","citation_count":12,"is_preprint":false},{"pmid":"29654549","id":"PMC_29654549","title":"Severe Leukoencephalopathy with Clinical Recovery Caused by Recessive BOLA3 Mutations.","date":"2018","source":"JIMD reports","url":"https://pubmed.ncbi.nlm.nih.gov/29654549","citation_count":11,"is_preprint":false},{"pmid":"34063696","id":"PMC_34063696","title":"Molecular Basis of Multiple Mitochondrial Dysfunctions Syndrome 2 Caused by CYS59TYR BOLA3 Mutation.","date":"2021","source":"International journal of molecular sciences","url":"https://pubmed.ncbi.nlm.nih.gov/34063696","citation_count":8,"is_preprint":false},{"pmid":"31486956","id":"PMC_31486956","title":"Reconstitution, characterization, and [2Fe-2S] cluster exchange reactivity of a holo human BOLA3 homodimer.","date":"2019","source":"Journal of biological inorganic chemistry : JBIC : a publication of the Society of Biological Inorganic Chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/31486956","citation_count":4,"is_preprint":false},{"pmid":"33693876","id":"PMC_33693876","title":"Biochemical impact of a disease-causing Ile67Asn substitution on BOLA3 protein.","date":"2021","source":"Metallomics : integrated biometal science","url":"https://pubmed.ncbi.nlm.nih.gov/33693876","citation_count":2,"is_preprint":false},{"pmid":"39455467","id":"PMC_39455467","title":"Dysregulated inclusion of BOLA3 exon 3 promoted by HNRNPC accelerates the progression of esophageal squamous cell carcinoma.","date":"2024","source":"Frontiers of medicine","url":"https://pubmed.ncbi.nlm.nih.gov/39455467","citation_count":1,"is_preprint":false},{"pmid":"37511493","id":"PMC_37511493","title":"Understanding the Molecular Basis of the Multiple Mitochondrial Dysfunctions Syndrome 2: The Disease-Causing His96Arg Mutation of BOLA3.","date":"2023","source":"International journal of molecular sciences","url":"https://pubmed.ncbi.nlm.nih.gov/37511493","citation_count":1,"is_preprint":false},{"pmid":"40850197","id":"PMC_40850197","title":"BOLA3 as a key protein for the treatment of diabetic skeletal muscle atrophy.","date":"2025","source":"International immunopharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/40850197","citation_count":0,"is_preprint":false},{"pmid":"40273865","id":"PMC_40273865","title":"Role of BOLA3 in the mitochondrial Fe-S cluster clarified by metabolomic analysis.","date":"2025","source":"Molecular genetics and metabolism","url":"https://pubmed.ncbi.nlm.nih.gov/40273865","citation_count":0,"is_preprint":false},{"pmid":"39849679","id":"PMC_39849679","title":"Exploring the potential of BOLA3-DT as a diagnostic biomarker in prostate cancer.","date":"2025","source":"Urologia","url":"https://pubmed.ncbi.nlm.nih.gov/39849679","citation_count":0,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":10554,"output_tokens":3110,"usd":0.039156},"stage2":{"model":"claude-opus-4-6","input_tokens":6457,"output_tokens":2447,"usd":0.14019},"total_usd":0.179346,"stage1_batch_id":"msgbatch_01TqNM6p6FsoMBT2jzQTwKBr","stage2_batch_id":"msgbatch_01Ya473eco8sTHbvRymQaU8o","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2011,\n      \"finding\": \"BOLA3 is required for the biogenesis of iron-sulfur ([Fe-S]) clusters necessary for normal maturation of lipoate-containing 2-oxoacid dehydrogenases and assembly of mitochondrial respiratory chain complexes I, II, and III. Retroviral transduction with the mitochondrial isoform 1 (but not isoform 2) of BOLA3 rescued both respiratory chain function and oxoacid dehydrogenase activity in patient fibroblasts.\",\n      \"method\": \"Retroviral complementation of patient fibroblasts with isoform-specific BOLA3 constructs; biochemical enzyme activity assays\",\n      \"journal\": \"American journal of human genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal isoform rescue experiment with defined biochemical phenotype, replicated by subsequent independent labs\",\n      \"pmids\": [\"21944046\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"A homozygous missense mutation in BOLA3 causes combined deficiency of respiratory chain complexes I, II, and II+III and pyruvate dehydrogenase complex; lentiviral expression of wild-type mitochondrial BOLA3 isoform in patient fibroblasts restored residual enzyme activities and lipoic acid levels, confirming BOLA3's role in Fe-S cluster biogenesis and lipoylation.\",\n      \"method\": \"Exome sequencing; lentiviral complementation; biochemical enzyme activity assays; lipoic acid quantification\",\n      \"journal\": \"Journal of inherited metabolic disease\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — independent replication of functional rescue with multiple biochemical readouts\",\n      \"pmids\": [\"22562699\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"BOLA3 mutations cause deficiency of lipoylation of mitochondrial proteins and deficient glycine cleavage enzyme activity, impacting lipoate-dependent enzymes including pyruvate dehydrogenase; transfection with native BOLA3 corrected the biochemical deficiency, demonstrating its essential role in lipoate biosynthesis.\",\n      \"method\": \"Genetic sequencing; cell transfection complementation; lipoylation assay; enzyme activity measurement\",\n      \"journal\": \"Brain : a journal of neurology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — complementation rescue with multiple enzyme readouts, independent cohort\",\n      \"pmids\": [\"24334290\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Human mitochondrial BOLA3 forms a [2Fe-2S] cluster-bridged dimeric heterocomplex with the monothiol glutaredoxin GRX5. The BOLA3-GRX5 complex coordinates an oxidized, ferredoxin-like [2Fe-2S]2+ cluster, in contrast to the reduced Rieske-type [2Fe-2S]1+ cluster found in the BOLA1-GRX5 complex. The BOLA1-GRX5 complex has higher cluster binding affinity than BOLA3-GRX5.\",\n      \"method\": \"UV/vis, CD, EPR, NMR spectroscopy; computational protein-protein docking; in vitro reconstitution of complexes\",\n      \"journal\": \"Biochimica et biophysica acta. General subjects\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — multiple orthogonal biophysical and spectroscopic methods with in vitro reconstitution\",\n      \"pmids\": [\"28483642\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"The [2Fe-2S] cluster-bridged BOLA3-GLRX5 heterocomplex functions as a cluster trafficking intermediate: apo BOLA3-glutaredoxin complexes accept [2Fe-2S] clusters from donors (ISCU and [2Fe-2S](GS)4), preferentially forming the heterodimer over the holo glutaredoxin homodimer; holo BOLA3-GLRX5 transfers clusters to apo acceptors at rates comparable to other Fe-S trafficking proteins. ITC confirmed strong binding of apo BOLA3 with GLRX5 and weak binding with NFU1.\",\n      \"method\": \"In vitro cluster transfer assays; isothermal titration calorimetry (ITC); UV/vis spectroscopy\",\n      \"journal\": \"Metallomics : integrated biometal science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — reconstituted in vitro cluster exchange with quantitative binding data and kinetics\",\n      \"pmids\": [\"30137089\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Human BOLA3 can form a functional [2Fe-2S]-bridged homodimer capable of Fe-S cluster binding and inter-protein cluster transfer, in addition to its known heterodimeric interactions with GLRX5 and NFU1.\",\n      \"method\": \"In vitro reconstitution; spectroscopic characterization; cluster transfer assays\",\n      \"journal\": \"Journal of biological inorganic chemistry : JBIC\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 — in vitro reconstitution, single lab\",\n      \"pmids\": [\"31486956\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"The disease-causing Ile67Asn substitution in BOLA3 impairs the ability of BOLA3 to bind its physiological partner GLRX5 and prevents formation of the [2Fe-2S]-bridged heterocomplex, thereby blocking downstream cluster reconstitution, without causing major overall structural changes to BOLA3 itself.\",\n      \"method\": \"1H-15N HSQC NMR; ion mobility native mass spectrometry; in vitro cluster reconstitution assays\",\n      \"journal\": \"Metallomics : integrated biometal science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — multiple orthogonal methods (NMR, native MS, cluster assays) with disease-relevant mutagenesis\",\n      \"pmids\": [\"33693876\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"The Cys59Tyr BOLA3 mutation structurally perturbs the [2Fe-2S] cluster-binding region of BOLA3 without abolishing cluster binding on the BOLA3-GLRX5 heterocomplex; Tyr59 does not replace Cys59 as a cluster ligand, but promotes formation of an aberrant apo BOLA3-GLRX5 complex, explaining the unique milder clinical phenotype.\",\n      \"method\": \"NMR; UV/vis, CD, EPR spectroscopy; experimentally driven molecular docking; size exclusion chromatography\",\n      \"journal\": \"International journal of molecular sciences\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — multiple orthogonal spectroscopic and structural methods with mechanistic mutagenesis validation\",\n      \"pmids\": [\"34063696\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"BOLA3 deficiency in beige adipocytes inhibits thermogenesis by impairing mitochondrial homeostasis (reduced respiratory chain complexes and mitochondrial formation) and adrenergic signaling-induced lipolysis, without affecting lipogenesis.\",\n      \"method\": \"Lentiviral shRNA knockdown in differentiated beige adipocytes; Seahorse respirometry; Western blot for respiratory chain complexes; lipolysis assay\",\n      \"journal\": \"Frontiers in endocrinology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — clean KD with defined cellular phenotypes, single lab\",\n      \"pmids\": [\"33505355\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"The His96Arg BOLA3 mutation does not impair BOLA3-GLRX5 interaction but leads to an aberrant [2Fe-2S]-BOLA3-GLRX5 heterocomplex that cannot assemble a [4Fe-4S] cluster on NFU1, establishing that His96 is a critical [2Fe-2S] cluster ligand in the BOLA3-GLRX5 complex and that [4Fe-4S] delivery to NFU1 is downstream of the BOLA3-GLRX5 node.\",\n      \"method\": \"Size exclusion chromatography; NMR; UV/vis; CD; EPR spectroscopy; in vitro [4Fe-4S] cluster assembly assay on NFU1\",\n      \"journal\": \"International journal of molecular sciences\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — multiple orthogonal methods, disease mutation used to establish mechanistic pathway step\",\n      \"pmids\": [\"37511493\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"The mitoribosome receives its [2Fe-2S] clusters from the GLRX5-BOLA3 node; loss of BOLA3 attenuates mitochondrial protein synthesis through impaired [2Fe-2S] cluster assembly into the mitoribosome small subunit. One of the mitoribosomal [2Fe-2S] clusters senses changes in the redox environment, providing a regulatory mechanism for organellar protein synthesis.\",\n      \"method\": \"siRNA silencing of Fe-S cluster biosynthetic factors; mitoribosome stability assays; mitochondrial protein synthesis assays in BOLA3-mutant patient fibroblasts; structure-function correlation studies\",\n      \"journal\": \"Nucleic acids research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple complementary experiments in human patient fibroblasts and siRNA knockdowns with defined mechanistic readouts\",\n      \"pmids\": [\"37823603\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Metabolomic analysis of BOLA3-deficient patient fibroblasts shows elevated lactic acid, pyruvic acid, TCA cycle intermediates (α-ketoglutaric acid, succinic acid), branched-chain amino acids, and lysine/tryptophan metabolites, with near-absent complex I and II bands; aconitase activity is unaffected. This defines BOLA3 as specifically involved in [4Fe-4S] cluster delivery to respiratory chain complexes I and II and lipoic acid synthetase, but not aconitase.\",\n      \"method\": \"Capillary electrophoresis time-of-flight mass spectrometry metabolomics; BN-PAGE/Western blot; in-gel enzyme staining of mitochondrial complexes in patient fibroblasts\",\n      \"journal\": \"Molecular genetics and metabolism\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — multi-method biochemical analysis in patient cells defining pathway specificity, single lab\",\n      \"pmids\": [\"40273865\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"BOLA3 is a mitochondrial protein that forms a [2Fe-2S] cluster-bridged heterocomplex with the monothiol glutaredoxin GLRX5 (coordinating an oxidized ferredoxin-like [2Fe-2S]2+ cluster), which serves as an intermediate node for trafficking [2Fe-2S] clusters to the mitoribosome and for assembling [4Fe-4S] clusters on NFU1, thereby enabling maturation of respiratory chain complexes I and II, lipoic acid synthetase (and thus lipoate-dependent 2-oxoacid dehydrogenases), and mitoribosomal subunits; loss of BOLA3 function simultaneously impairs mitochondrial protein synthesis, respiratory chain activity, and lipoylation-dependent enzyme activities.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"BOLA3 is a mitochondrial iron-sulfur (Fe-S) cluster trafficking factor that bridges Fe-S cluster biogenesis to the maturation of respiratory chain complexes, lipoic acid-dependent enzymes, and the mitoribosome. BOLA3 forms a [2Fe-2S] cluster-bridged heterocomplex with the monothiol glutaredoxin GLRX5, which accepts clusters from upstream donors (ISCU) and delivers them downstream to NFU1 for [4Fe-4S] cluster assembly on respiratory chain complexes I and II and lipoic acid synthetase, as well as directly to the mitoribosome small subunit for mitochondrial protein synthesis [PMID:28483642, PMID:30137089, PMID:37511493, PMID:37823603]. Disease-causing mutations in BOLA3 (e.g., Ile67Asn, His96Arg) disrupt either GLRX5 binding or cluster coordination within the heterocomplex, abolishing downstream [4Fe-4S] assembly on NFU1 and causing combined deficiency of respiratory chain complexes I, II, and III, pyruvate dehydrogenase, glycine cleavage enzyme, and lipoylation, while sparing aconitase [PMID:33693876, PMID:37511493, PMID:40273865]. Biallelic loss-of-function mutations in BOLA3 cause multiple mitochondrial dysfunctions syndrome type 2 (MMDS2), a severe disorder characterized by combined respiratory chain and lipoylation defects [PMID:21944046, PMID:22562699, PMID:24334290].\",\n  \"teleology\": [\n    {\n      \"year\": 2011,\n      \"claim\": \"Establishing that BOLA3 is essential for Fe-S cluster-dependent maturation of respiratory chain complexes and lipoate-containing enzymes resolved the genetic basis of a combined mitochondrial dysfunction syndrome and identified a new Fe-S biogenesis factor.\",\n      \"evidence\": \"Retroviral complementation of BOLA3-mutant patient fibroblasts with isoform-specific constructs; biochemical enzyme assays\",\n      \"pmids\": [\"21944046\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular mechanism of BOLA3 action unknown\", \"Direct protein partners unidentified\", \"Whether BOLA3 acts at [2Fe-2S] or [4Fe-4S] stage undetermined\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Independent replication confirmed BOLA3 loss causes combined respiratory chain and lipoylation deficiency, and demonstrated that wild-type BOLA3 restores lipoic acid levels, cementing the link between Fe-S biogenesis and lipoate biosynthesis.\",\n      \"evidence\": \"Exome sequencing of new patients; lentiviral complementation; lipoic acid quantification in patient fibroblasts\",\n      \"pmids\": [\"22562699\", \"24334290\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Physical interaction partners not identified\", \"Whether glycine cleavage system impairment is direct or indirect through lipoylation unclear\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Biophysical reconstitution of the BOLA3-GLRX5 [2Fe-2S]-bridged heterocomplex defined the molecular species through which BOLA3 acts, revealing it coordinates an oxidized ferredoxin-like [2Fe-2S]²⁺ cluster distinct from the BOLA1-GLRX5 complex.\",\n      \"evidence\": \"UV/vis, CD, EPR, NMR spectroscopy and computational docking of purified human proteins\",\n      \"pmids\": [\"28483642\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direction of cluster flow (donor vs. acceptor) not yet demonstrated\", \"In vivo relevance of heterocomplex not confirmed\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Quantitative in vitro cluster transfer experiments established that the BOLA3-GLRX5 heterocomplex functions as a bona fide trafficking intermediate, accepting [2Fe-2S] clusters from ISCU and transferring them to downstream acceptors, and revealed weak binding of apo BOLA3 to NFU1.\",\n      \"evidence\": \"In vitro cluster transfer kinetics; isothermal titration calorimetry; UV/vis spectroscopy\",\n      \"pmids\": [\"30137089\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether BOLA3-GLRX5 directly provides clusters to NFU1 for [4Fe-4S] assembly not shown\", \"BOLA3 homodimer physiological relevance unclear\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Structural and biochemical analysis of disease-causing mutations (Ile67Asn, Cys59Tyr) revealed that pathogenicity operates through distinct mechanisms — loss of GLRX5 binding versus perturbation of the cluster-binding site — explaining genotype-phenotype variability.\",\n      \"evidence\": \"NMR, native MS, EPR spectroscopy, and in vitro cluster reconstitution with mutant BOLA3 proteins\",\n      \"pmids\": [\"33693876\", \"34063696\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"In vivo validation of mutant complex formation not performed\", \"Whether aberrant apo complex has gain-of-function effects unknown\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"The His96Arg mutation demonstrated that His96 is a critical [2Fe-2S] cluster ligand in the heterocomplex and that [4Fe-4S] cluster assembly on NFU1 lies directly downstream of the BOLA3-GLRX5 node, ordering the pathway from [2Fe-2S] trafficking to [4Fe-4S] maturation.\",\n      \"evidence\": \"Size exclusion chromatography, NMR, EPR, CD spectroscopy, and in vitro [4Fe-4S] cluster assembly assay on NFU1\",\n      \"pmids\": [\"37511493\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Complete set of cluster ligands in the heterocomplex not fully resolved\", \"Whether BOLA3-GLRX5 directly donates to NFU1 or requires additional intermediates in vivo unknown\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Discovery that the mitoribosome receives [2Fe-2S] clusters from the GLRX5-BOLA3 node expanded BOLA3 function beyond respiratory chain and lipoylation to mitochondrial translation, and revealed redox-sensing by a mitoribosomal [2Fe-2S] cluster as a regulatory mechanism.\",\n      \"evidence\": \"siRNA knockdown of Fe-S factors; mitoribosome stability and translation assays in BOLA3-mutant patient fibroblasts\",\n      \"pmids\": [\"37823603\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Identity of the mitoribosomal [2Fe-2S] acceptor protein not specified\", \"Whether translation defect contributes to respiratory chain loss or is independent phenotype unclear\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Metabolomic profiling of BOLA3-deficient cells defined pathway specificity: BOLA3 is required for [4Fe-4S] delivery to complexes I, II, and lipoic acid synthetase but not for aconitase maturation, distinguishing BOLA3 from other late-acting Fe-S factors.\",\n      \"evidence\": \"CE-TOF-MS metabolomics, BN-PAGE, and in-gel enzyme activity in patient fibroblasts\",\n      \"pmids\": [\"40273865\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism by which aconitase escapes BOLA3 dependence not explained\", \"Single-lab metabolomic study without independent replication\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"The structural basis of the intact [2Fe-2S]-BOLA3-GLRX5 heterocomplex, the mechanism by which it selectively delivers clusters to NFU1 versus the mitoribosome, and whether the BOLA3 homodimer has a physiological role remain unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No high-resolution structure of the holo BOLA3-GLRX5 heterocomplex\", \"Selectivity mechanism for [2Fe-2S] delivery to mitoribosome vs. NFU1 unknown\", \"Physiological relevance of BOLA3 homodimer not established in vivo\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140104\", \"supporting_discovery_ids\": [3, 4, 9, 10]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005739\", \"supporting_discovery_ids\": [0, 1, 2, 3, 10]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-1430728\", \"supporting_discovery_ids\": [0, 1, 2, 4, 9, 11]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [0, 1, 6, 7]}\n    ],\n    \"complexes\": [\n      \"BOLA3-GLRX5 [2Fe-2S]-bridged heterocomplex\"\n    ],\n    \"partners\": [\n      \"GLRX5\",\n      \"NFU1\",\n      \"ISCU\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}