Affinage

BOLA3

BolA-like protein 3 · UniProt Q53S33

Length
107 aa
Mass
12.1 kDa
Annotated
2026-06-09
18 papers in source corpus 12 papers cited in narrative 12 extracted findings
Cross-family judge vs UniProt: Affinage preferred faithfulness: 5/5 claims corpus-supported (100%)

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

BOLA3 (mitochondrial isoform 1) is an iron-sulfur cluster trafficking factor required for biogenesis of the Fe-S centers that mature lipoate-containing 2-oxoacid dehydrogenases and assemble mitochondrial respiratory chain complexes; isoform-specific patient-fibroblast complementation established that only the mitochondrial isoform restores combined respiratory chain and 2-oxoacid dehydrogenase deficiency (PMID:21944046, PMID:22562699). Mechanistically, BOLA3 forms a [2Fe-2S]2+ cluster-bridged heterocomplex with the monothiol glutaredoxin GLRX5, binding GLRX5 with high affinity while interacting only weakly with NFU1, marking GLRX5 as its physiological partner (PMID:28483642, PMID:30137089). This holo BOLA3-GLRX5 node accepts [2Fe-2S] clusters from donors such as ISCU and transfers them onward (PMID:30137089), serving as the intermediate for assembling [4Fe-4S] clusters on downstream targets including NFU1, and is functionally required for delivery of [4Fe-4S] clusters to respiratory complexes I and II and to lipoic acid synthase, but not to aconitase (PMID:37511493, PMID:40273865). Through this node BOLA3 also supplies the [2Fe-2S] cluster of the mitoribosome, with its loss impairing mitoribosome stability and mitochondrial protein synthesis (PMID:37823603). Disease-causing mutations partition by mechanism: I67N abolishes GLRX5 binding without altering BOLA3 structure, whereas C59Y and H96R preserve heterocomplex formation but yield aberrant complexes defective in downstream [4Fe-4S] assembly, with H96 identified as a cluster ligand (PMID:33693876, PMID:34063696, PMID:37511493).

Mechanistic history

Synthesis pass · year-by-year structured walk · 9 steps
  1. 2011 High

    Established that BOLA3 is required for mitochondrial Fe-S center biogenesis and that this function is specific to the mitochondrial isoform, defining the gene's compartment and essential role.

    Evidence Isoform-specific retroviral complementation of patient fibroblasts with biochemical respiratory chain and 2-oxoacid dehydrogenase readouts

    PMID:21944046

    Open questions at the time
    • Did not identify direct molecular partners or cluster type
    • Mechanism of cluster delivery unresolved
  2. 2012 High

    Independently confirmed the link between BOLA3 deficiency and impaired lipoylation plus respiratory function, anchoring the disease mechanism through functional rescue.

    Evidence Exome sequencing plus lentiviral complementation with measurement of complex activities and lipoic acid levels

    PMID:22562699

    Open questions at the time
    • No biochemical reconstitution of the trafficking step
    • Partner proteins not defined
  3. 2013 High

    Refined the phenotype by showing the primary defect is deficient mitochondrial protein lipoylation and reduced pyruvate dehydrogenase activity, with comparatively preserved respiratory chain and iron handling in this cohort.

    Evidence Patient fibroblast transfection complementation with lipoate immunoblotting and enzyme assays

    PMID:24334290

    Open questions at the time
    • Cohort heterogeneity in respiratory phenotype unexplained
    • Direct cluster-handling mechanism not addressed
  4. 2017 High

    Identified the physical and chemical nature of BOLA3's functional unit by showing it bridges an oxidized ferredoxin-like [2Fe-2S]2+ cluster with GLRX5, distinguishing it from the BOLA1-GLRX5 complex.

    Evidence UV/vis, CD, EPR and NMR spectroscopy plus protein-protein docking, comparing BOLA1- and BOLA3-GLRX5 complexes

    PMID:28483642

    Open questions at the time
    • In vitro only; physiological occupancy not measured
    • Donor and acceptor proteins not yet defined
  5. 2018 High

    Demonstrated the node is competent for cluster traffic and that GLRX5, not NFU1, is the preferred binding partner, establishing the directionality of the pathway.

    Evidence In vitro cluster exchange kinetics and isothermal titration calorimetry with ISCU and glutathione-complexed cluster donors

    PMID:30137089

    Open questions at the time
    • Physiological donor in cells not confirmed
    • Identity of all downstream acceptors incomplete
  6. 2019 Medium

    Showed BOLA3 has intrinsic cluster-binding and transfer activity as a homodimer, indicating partner-independent trafficking capability.

    Evidence In vitro reconstitution of holo BOLA3 homodimer with cluster binding and exchange assays

    PMID:31486956

    Open questions at the time
    • Not independently replicated
    • Physiological relevance of homodimer versus GLRX5 heterocomplex unclear
  7. 2021 High

    Resolved how distinct disease mutations cause loss of function at separable steps: disrupting GLRX5 binding (I67N) versus perturbing the cluster-binding region while retaining binding (C59Y), rationalizing phenotype severity.

    Evidence In vitro reconstitution, HSQC NMR, ion mobility native MS, and spectroscopy comparing wild-type and mutant BOLA3

    PMID:33693876 PMID:34063696

    Open questions at the time
    • Cellular consequences inferred from in vitro behavior
    • Quantitative genotype-phenotype mapping limited
  8. 2023 High

    Connected BOLA3 to mitochondrial translation by showing the GLRX5-BOLA3 node supplies the mitoribosomal [2Fe-2S] cluster and that His96 is a cluster ligand required for downstream [4Fe-4S] assembly on NFU1.

    Evidence siRNA silencing with mitoribosome stability and protein synthesis assays in patient fibroblasts; spectroscopy and in vitro [4Fe-4S] assembly on NFU1

    PMID:37511493 PMID:37823603

    Open questions at the time
    • Direct structural docking of node onto mitoribosome not shown
    • Stoichiometry of cluster handoff in vivo unresolved
  9. 2025 Medium

    Defined substrate specificity of the pathway by showing BOLA3 is required for [4Fe-4S] delivery to complexes I and II and lipoic acid synthase but not aconitase, with characteristic metabolomic signatures.

    Evidence Capillary electrophoresis TOF-MS metabolomics and BN-PAGE/in-gel enzyme staining in eight patient fibroblast lines

    PMID:40273865

    Open questions at the time
    • Mechanistic basis for sparing of aconitase not established
    • Single-lab cohort

Open questions

Synthesis pass · forward-looking unresolved questions
  • How the BOLA3-GLRX5 node is physically targeted to and discharges clusters onto specific acceptors (mitoribosome, NFU1, lipoic acid synthase) while sparing others such as aconitase remains unresolved.
  • No structure of node bound to an acceptor
  • Determinants of acceptor selectivity unknown
  • In vivo cluster flux not quantified

Mechanism profile

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0140104 molecular carrier activity 4
Localization
GO:0005739 mitochondrion 3
Pathway
R-HSA-1430728 Metabolism 3 R-HSA-8953854 Metabolism of RNA 1
Partners
GLRX5ISCUNFU1
Complex memberships
BOLA3-GLRX5 [2Fe-2S] heterocomplex

Evidence

Reading pass · 12 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
2011 BOLA3 (mitochondrial isoform 1, not cytosolic isoform 2) is essential for biogenesis of [Fe-S] centers required for normal maturation of lipoate-containing 2-oxoacid dehydrogenases and assembly of mitochondrial respiratory chain complexes I, II, and III. Loss-of-function frameshift mutation (c.123dupA) caused combined deficiency; rescue by retroviral expression of mitochondrial isoform 1 but not isoform 2 restored respiratory chain and oxoacid dehydrogenase function. Patient fibroblast complementation with retroviral vectors expressing isoform-specific BOLA3 constructs; biochemical assays of respiratory chain and 2-oxoacid dehydrogenase activities American journal of human genetics High 21944046
2012 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 in patient fibroblasts restored residual enzyme activities and lipoic acid levels, demonstrating BOLA3's role in Fe-S cluster biogenesis required for lipoylation and respiratory function. Exome sequencing; lentiviral complementation of patient fibroblasts; biochemical measurement of respiratory chain complex activities and lipoic acid levels Journal of inherited metabolic disease High 22562699
2013 BOLA3 mutations cause deficient lipoylation of mitochondrial proteins and reduced pyruvate dehydrogenase enzyme activity; transfection with wild-type BOLA3 corrected the biochemical deficiency in patient cells, confirming BOLA3's role in lipoate biosynthesis (downstream of Fe-S cluster biogenesis). Respiratory chain activity was largely unaffected in BOLA3-mutant patients in this cohort (unlike NFU1 cases), and cellular iron handling was minimally changed. Patient fibroblast transfection complementation; biochemical assays of lipoylation, glycine cleavage enzyme, and pyruvate dehydrogenase; lipoate immunoblotting Brain : a journal of neurology High 24334290
2017 Human mitochondrial BOLA3 forms a [2Fe-2S] cluster-bridged dimeric heterocomplex with monothiol glutaredoxin GRX5. In this complex, BOLA3-GRX5 coordinates an oxidized, ferredoxin-like [2Fe-2S]2+ cluster, in contrast to the reduced, Rieske-type [2Fe-2S]1+ cluster in BOLA1-GRX5. The BOLA1-GRX5 complex has higher cluster binding affinity and is preferentially formed over BOLA3-GRX5. UV/vis, CD, EPR and NMR spectroscopies; computational protein-protein docking; comparison of [2Fe-2S] cluster oxidation states between BOLA1-GRX5 and BOLA3-GRX5 complexes Biochimica et biophysica acta. General subjects High 28483642
2018 Holo BOLA3-GLRX5 heterocomplex can accept [2Fe-2S] clusters from donors (ISCU and [2Fe-2S](GS)4) and transfer clusters to apo acceptors at rates comparable to other Fe-S trafficking proteins. Apo BOLA3 binds tightly to GLRX5 and S. cerevisiae Grx3 (isothermal titration calorimetry), whereas binding to NFU1 was weak, supporting GLRX5 rather than NFU1 as the physiological partner. Preferential formation of the heterodimer over holo homodimeric glutaredoxin was observed. In vitro cluster exchange assays (UV/vis kinetics); isothermal titration calorimetry (ITC); use of ISCU and glutathione-complexed cluster as donors; comparison with yeast Grx3 Metallomics : integrated biometal science High 30137089
2019 Human BOLA3 can form a functional homodimer that binds a [2Fe-2S] cluster and is capable of Fe-S cluster transfer to apo acceptors, demonstrating that BOLA3 itself has intrinsic cluster-binding and trafficking activity independent of a GLRX5 partner. In vitro reconstitution of holo BOLA3 homodimer; biochemical characterization of Fe-S cluster binding and cluster exchange activity Journal of biological inorganic chemistry Medium 31486956
2021 The disease-causing Ile67Asn substitution in BOLA3 impairs its ability to bind GLRX5 and form the [2Fe-2S]-bridged heterocomplex, thereby blocking downstream cluster reconstitution on target proteins. The substitution causes no major structural change in BOLA3 itself (confirmed by 1H-15N HSQC NMR and ion mobility native MS), but specifically disrupts the protein-protein interaction required for cluster delivery. In vitro reconstitution; 1H-15N HSQC NMR; ion mobility native mass spectrometry; cluster exchange assays with wild-type vs. I67N BOLA3 Metallomics : integrated biometal science High 33693876
2021 The disease-causing Cys59Tyr mutation structurally perturbs the Fe-S cluster-binding region of BOLA3 but does not abolish [2Fe-2S]2+ cluster binding on the BOLA3-GLRX5 heterocomplex; Tyr59 does not replace Cys59 as an Fe-S cluster ligand; instead the mutation promotes formation of an aberrant apo BOLA3-GLRX5 complex, rationalizing a milder clinical phenotype. NMR spectroscopy; UV/vis, CD, EPR spectroscopy; experimentally driven molecular docking; size exclusion chromatography International journal of molecular sciences High 34063696
2021 BOLA3 knockdown in beige adipocytes inhibits thermogenesis by impairing mitochondrial homeostasis (decreased expression of mitochondria-related genes and respiratory chain complexes, attenuated mitochondrial biogenesis, reduced maximal respiration) and inhibiting isoproterenol-stimulated lipolysis, without affecting lipogenesis. Lentiviral shRNA knockdown in differentiated beige adipocytes; Seahorse respirometry; mitochondrial staining; gene expression analysis; lipolysis assay Frontiers in endocrinology Medium 33505355
2023 The disease-causing His96Arg mutation of BOLA3 does not impair formation of the BOLA3-GLRX5 heterocomplex but leads to an aberrant BOLA3-[2Fe-2S]-GLRX5 complex that is non-functional in assembling a [4Fe-4S] cluster on NFU1, establishing His96 as a [2Fe-2S] cluster ligand whose integrity is required for downstream [4Fe-4S] cluster assembly. Size exclusion chromatography; NMR, UV-visible, CD, and EPR spectroscopy; in vitro [4Fe-4S] cluster assembly assay on NFU1 International journal of molecular sciences High 37511493
2023 The mitoribosome receives its [2Fe-2S] clusters from the GLRX5-BOLA3 node. Silencing BOLA3 (or NFU1) impairs mitoribosome stability and attenuates mitochondrial protein synthesis in patient fibroblasts with MMDS2. One mitoribosomal [2Fe-2S] cluster and a METTL17 [4Fe-4S] cluster act as redox sensors to regulate organellar protein synthesis in response to redox changes. siRNA silencing of Fe-S biosynthetic factors; analysis of mitoribosome stability and protein synthesis in patient fibroblasts; structure-function correlation studies; analysis of METTL17 cluster content Nucleic acids research High 37823603
2025 Metabolomic analysis of BOLA3-variant patient fibroblasts reveals elevated lactic acid, pyruvic acid, alanine, TCA cycle intermediates (α-ketoglutaric acid, succinic acid), branched-chain amino acids, and lysine/tryptophan metabolites, while BN-PAGE shows near-absent complex I and II bands; BOLA3 is functionally required for [4Fe-4S] cluster delivery to respiratory chain complexes I and II and lipoic acid synthase, but not to aconitase. Capillary electrophoresis time-of-flight mass spectrometry metabolomics; blue native PAGE/Western blot; in-gel enzyme staining of respiratory chain complexes; patient fibroblasts from eight individuals Molecular genetics and metabolism Medium 40273865

Source papers

Stage 0 corpus · 18 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
2011 Mutations in iron-sulfur cluster scaffold genes NFU1 and BOLA3 cause a fatal deficiency of multiple respiratory chain and 2-oxoacid dehydrogenase enzymes. American journal of human genetics 223 21944046
2013 Variant non ketotic hyperglycinemia is caused by mutations in LIAS, BOLA3 and the novel gene GLRX5. Brain : a journal of neurology 170 24334290
2012 Homozygous missense mutation in BOLA3 causes multiple mitochondrial dysfunctions syndrome in two siblings. Journal of inherited metabolic disease 76 22562699
2017 Structural insights into the molecular function of human [2Fe-2S] BOLA1-GRX5 and [2Fe-2S] BOLA3-GRX5 complexes. Biochimica et biophysica acta. General subjects 44 28483642
2023 BOLA3 and NFU1 link mitoribosome iron-sulfur cluster assembly to multiple mitochondrial dysfunctions syndrome. Nucleic acids research 29 37823603
2018 Cluster exchange reactivity of [2Fe-2S] cluster-bridged complexes of BOLA3 with monothiol glutaredoxins. Metallomics : integrated biometal science 20 30137089
2018 An infant case of diffuse cerebrospinal lesions and cardiomyopathy caused by a BOLA3 mutation. Brain & development 19 29501406
2021 Bola3 Regulates Beige Adipocyte Thermogenesis via Maintaining Mitochondrial Homeostasis and Lipolysis. Frontiers in endocrinology 13 33505355
2018 Imaging phenotype of multiple mitochondrial dysfunction syndrome 2, a rare BOLA3-associated leukodystrophy. American journal of medical genetics. Part A 13 30302924
2018 Severe Leukoencephalopathy with Clinical Recovery Caused by Recessive BOLA3 Mutations. JIMD reports 11 29654549
2021 Molecular Basis of Multiple Mitochondrial Dysfunctions Syndrome 2 Caused by CYS59TYR BOLA3 Mutation. International journal of molecular sciences 8 34063696
2019 Reconstitution, characterization, and [2Fe-2S] cluster exchange reactivity of a holo human BOLA3 homodimer. Journal of biological inorganic chemistry : JBIC : a publication of the Society of Biological Inorganic Chemistry 4 31486956
2024 Dysregulated inclusion of BOLA3 exon 3 promoted by HNRNPC accelerates the progression of esophageal squamous cell carcinoma. Frontiers of medicine 2 39455467
2021 Biochemical impact of a disease-causing Ile67Asn substitution on BOLA3 protein. Metallomics : integrated biometal science 2 33693876
2025 Role of BOLA3 in the mitochondrial Fe-S cluster clarified by metabolomic analysis. Molecular genetics and metabolism 1 40273865
2025 BOLA3 as a key protein for the treatment of diabetic skeletal muscle atrophy. International immunopharmacology 1 40850197
2023 Understanding the Molecular Basis of the Multiple Mitochondrial Dysfunctions Syndrome 2: The Disease-Causing His96Arg Mutation of BOLA3. International journal of molecular sciences 1 37511493
2025 Exploring the potential of BOLA3-DT as a diagnostic biomarker in prostate cancer. Urologia 0 39849679

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