BOLA3 is a mitochondrial BolA-family protein that functions as a late-acting iron-sulfur (Fe-S) cluster assembly factor. BOLA3 forms a heterocomplex with the mitochondrial monothiol glutaredoxin GLRX5, bridged by a [2Fe-2S] cluster (coordinated by BOLA3 Cys59 and His96, and GLRX5 Cys67 plus glutathione). This GLRX5-BOLA3 complex acts as a [2Fe-2S] carrier/chaperone that delivers cluster equivalents to NFU1, where two [2Fe-2S] clusters are converted to a [4Fe-4S] cluster for insertion into downstream client proteins including lipoyl synthase (LIAS), succinate dehydrogenase, and the mitoribosome. BOLA3 deficiency causes Multiple Mitochondrial Dysfunctions Syndrome type 2 (MMDS2), characterized by defective protein lipoylation, impaired respiratory chain complex activities, and attenuated mitochondrial translation.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
|
GO:0051604
protein maturation
|
IBA
GO_REF:0000033 |
MODIFY |
Summary: This annotation captures BOLA3's role in facilitating Fe-S cluster insertion into mitochondrial proteins, which is a form of protein maturation. BOLA3 functions in the late ISC pathway to enable [4Fe-4S] protein maturation (PMID:27532772).
Reason: While "protein maturation" is technically accurate, it is too general. BOLA3 specifically functions in iron-sulfur cluster assembly and insertion. More precise terms exist that better describe the molecular function.
Proposed replacements:
iron-sulfur cluster assembly
[4Fe-4S] cluster assembly
Supporting Evidence:
PMID:27532772
Bol1 and Bol3 as specific mitochondrial ISC assembly factors that facilitate [4Fe-4S] cluster insertion into a subset of mitochondrial proteins such as lipoate synthase and succinate dehydrogenase
file:human/BOLA3/BOLA3-deep-research-falcon.md
model: Edison Scientific Literature
|
|
GO:0005759
mitochondrial matrix
|
IBA
GO_REF:0000033 |
ACCEPT |
Summary: BOLA3 localizes to mitochondria where it functions in the mitochondrial ISC assembly pathway. Multiple lines of evidence support mitochondrial localization (PMID:22746225, PMID:27532772).
Reason: The mitochondrial matrix localization is well-supported by phylogenetic inference (IBA) and is consistent with experimental data. BOLA3 functions within the mitochondrial ISC pathway alongside GLRX5 and NFU1.
Supporting Evidence:
PMID:22746225
BOLA1 is a mitochondrial protein
PMID:27532772
Mitochondrial Bol1 and Bol3 function as assembly factors for specific iron-sulfur proteins
|
|
GO:0005739
mitochondrion
|
IEA
GO_REF:0000120 |
ACCEPT |
Summary: Automated annotation of mitochondrial localization is correct and consistent with experimental data showing BOLA3 is a mitochondrial protein (PMID:22746225).
Reason: This IEA annotation is broader than the IBA to mitochondrial matrix but is not incorrect. Multiple annotations at different specificity levels are acceptable.
Supporting Evidence:
PMID:22746225
We show that BOLA1 is a mitochondrial protein
|
|
GO:0005515
protein binding
|
IPI
PMID:27499296 Mitochondrial Protein Interaction Mapping Identifies Regulat... |
MODIFY |
Summary: This annotation captures interaction with GLRX5 from a mitochondrial protein interaction mapping study. The interaction is functionally significant.
Reason: "Protein binding" is too vague and uninformative. BOLA3 specifically binds GLRX5 to form a Fe-S cluster-bridged heterocomplex. A more informative MF term should be used.
Proposed replacements:
2 iron, 2 sulfur cluster binding
Supporting Evidence:
PMID:27532772
BOLA1 or BOLA3 and GLRX5 at the atomic level
PMID:27499296
2016 Aug 4. Mitochondrial Protein Interaction Mapping Identifies Regulators of Respiratory Chain Function.
|
|
GO:0005515
protein binding
|
IPI
PMID:27532772 Mitochondrial Bol1 and Bol3 function as assembly factors for... |
MODIFY |
Summary: This annotation reflects the physical interaction between BOLA3 and GLRX5 demonstrated by NMR spectroscopy. BOLA3 forms a [2Fe-2S]-bridged heterocomplex with GLRX5, with BOLA3 Cys59 and His96 serving as cluster ligands (PMID:27532772).
Reason: "Protein binding" does not capture the specific nature of the BOLA3-GLRX5 interaction. The interaction involves forming a Fe-S cluster-bridged complex essential for cluster transfer.
Proposed replacements:
2 iron, 2 sulfur cluster binding
Supporting Evidence:
PMID:27532772
The structures of (A) BOLA1 and (B) BOLA3 were solved by solution NMR. Residues His58, His67 and His102 are conserved within the eukaryotic BOLA1 proteins, and residues Cys59 and His96 are conserved within the BOLA3 proteins
|
|
GO:0005515
protein binding
|
IPI
PMID:32296183 A reference map of the human binary protein interactome. |
MARK AS OVER ANNOTATED |
Summary: High-throughput binary interactome mapping study. The specific interaction partners from this study include GLRX5.
Reason: Generic "protein binding" from HTP studies provides limited functional insight. The functionally relevant interactions (GLRX5, NFU1) are better captured through more specific annotations.
Supporting Evidence:
PMID:32296183
Apr 8. A reference map of the human binary protein interactome.
|
|
GO:0005515
protein binding
|
IPI
PMID:33961781 Dual proteome-scale networks reveal cell-specific remodeling... |
MARK AS OVER ANNOTATED |
Summary: Dual proteome-scale interactome study. This is a high-throughput study.
Reason: Generic "protein binding" from HTP proteome-scale studies is not informative for functional annotation. The core BOLA3-GLRX5 interaction is better captured with more specific terms.
Supporting Evidence:
PMID:33961781
2021 May 6. Dual proteome-scale networks reveal cell-specific remodeling of the human interactome.
|
|
GO:0005515
protein binding
|
IPI
PMID:34063696 Molecular Basis of Multiple Mitochondrial Dysfunctions Syndr... |
MODIFY |
Summary: This study examined the C59Y BOLA3 variant and demonstrated that the mutant still forms a heterocomplex with GLRX5, though with altered properties. The interaction between BOLA3 and GLRX5 involves [2Fe-2S] cluster coordination.
Reason: The study provides detailed molecular characterization of the BOLA3-GLRX5 interaction showing cluster binding. More specific terms should be used.
Proposed replacements:
2 iron, 2 sulfur cluster binding
Supporting Evidence:
PMID:34063696
C59Y BOLA3-GLRX5 Complex Bound a [2Fe-2S]2+ Cluster
|
|
GO:0005739
mitochondrion
|
IDA
GO_REF:0000052 |
ACCEPT |
Summary: HPA immunofluorescence data supporting mitochondrial localization.
Reason: Direct experimental evidence for mitochondrial localization is consistent with the known function of BOLA3 in the mitochondrial ISC assembly pathway.
|
|
GO:0005739
mitochondrion
|
NAS
PMID:22746225 BOLA1 is an aerobic protein that prevents mitochondrial morp... |
ACCEPT |
Summary: This study primarily characterized BOLA1 but also demonstrated that the BolA family proteins are mitochondrial. BOLA3 was mentioned in the context of mitochondrial Fe-S cluster biogenesis.
Reason: The study provides supporting evidence for mitochondrial localization of the BolA family proteins, consistent with their role in mitochondrial ISC assembly.
Supporting Evidence:
PMID:22746225
BOLA3 has recently been implicated in the biogenesis of [Fe-S] clusters for oxidative phosphorylation complexes and 2-oxo acid dehydrogenase enzymes in mitochondria
|
|
GO:0006879
intracellular iron ion homeostasis
|
NAS
PMID:27532772 Mitochondrial Bol1 and Bol3 function as assembly factors for... |
KEEP AS NON CORE |
Summary: The BOLA3-GLRX5 complex functions in Fe-S cluster assembly, which indirectly affects iron homeostasis. However, BOLA3's primary role is in Fe-S cluster biogenesis rather than direct iron sensing or trafficking.
Reason: While BOLA3 does influence iron homeostasis through its role in Fe-S cluster assembly, this is a downstream consequence rather than the core function. The primary role is in [4Fe-4S] cluster assembly.
Supporting Evidence:
PMID:27532772
Bol1 and Bol3 as specific mitochondrial ISC assembly factors
|
|
GO:0016226
iron-sulfur cluster assembly
|
NAS
PMID:27532772 Mitochondrial Bol1 and Bol3 function as assembly factors for... |
ACCEPT |
Summary: BOLA3 functions in the late phase of mitochondrial Fe-S cluster assembly, specifically facilitating [4Fe-4S] cluster insertion into target proteins. The GLRX5-BOLA3 complex delivers [2Fe-2S] clusters to NFU1 for [4Fe-4S] assembly (PMID:27532772).
Reason: This is a core function annotation. BOLA3 is a bona fide Fe-S cluster assembly factor as demonstrated by biochemical and genetic studies. The NAS evidence appropriately reflects the complex molecular pathway.
Supporting Evidence:
PMID:27532772
we characterize the BOLA family proteins Bol1 and Bol3 as specific mitochondrial ISC assembly factors that facilitate [4Fe-4S] cluster insertion into a subset of mitochondrial proteins such as lipoate synthase and succinate dehydrogenase
|
|
GO:0045454
cell redox homeostasis
|
NAS
PMID:27532772 Mitochondrial Bol1 and Bol3 function as assembly factors for... |
KEEP AS NON CORE |
Summary: BolA proteins interact with glutaredoxins and have been implicated in redox regulation. However, the primary characterized function of BOLA3 is in Fe-S cluster assembly rather than direct redox regulation.
Reason: This annotation likely reflects the association with GLRX5, a glutaredoxin. While the BOLA3-GLRX5 interaction is functionally important, the primary role is in Fe-S cluster transfer rather than redox homeostasis per se.
Supporting Evidence:
PMID:22746225
A measured interaction of BOLA1 with the mitochondrial monothiol glutaredoxin GLRX5 provides hints for potential mechanisms behind BOLA1's effect on mitochondrial redox potential
PMID:27532772
Mitochondrial Bol1 and Bol3 function as assembly factors for specific iron-sulfur proteins.
|
|
GO:0005739
mitochondrion
|
HTP
PMID:34800366 Quantitative high-confidence human mitochondrial proteome an... |
ACCEPT |
Summary: High-confidence human mitochondrial proteome study confirms mitochondrial localization.
Reason: HTP proteomics evidence is consistent with other evidence for mitochondrial localization of BOLA3.
Supporting Evidence:
PMID:34800366
Epub 2021 Nov 19. Quantitative high-confidence human mitochondrial proteome and its dynamics in cellular context.
|
|
GO:0005739
mitochondrion
|
IDA
PMID:22746225 BOLA1 is an aerobic protein that prevents mitochondrial morp... |
ACCEPT |
Summary: Direct experimental evidence from the Willems et al. study that characterized BolA family proteins as mitochondrial.
Reason: IDA evidence for mitochondrial localization is well-supported and consistent with BOLA3's role in the mitochondrial ISC pathway.
Supporting Evidence:
PMID:22746225
BOLA1 is a mitochondrial protein
|
|
GO:0051537
2 iron, 2 sulfur cluster binding
|
IDA
PMID:27532772 Mitochondrial Bol1 and Bol3 function as assembly factors for... |
NEW |
Summary: BOLA3 binds a [2Fe-2S] cluster as part of the GLRX5-BOLA3 heterocomplex. NMR and spectroscopic studies demonstrate that BOLA3 Cys59 and His96 serve as cluster ligands (PMID:27532772, PMID:34063696).
Reason: This is a core molecular function that is well-characterized but not present in the current annotation set. The [2Fe-2S] cluster binding is essential for BOLA3's function as a cluster carrier.
Supporting Evidence:
PMID:27532772
residues Cys59 and His96 are conserved within the BOLA3 proteins
PMID:34063696
C59Y BOLA3-GLRX5 Complex Bound a [2Fe-2S]2+ Cluster
|
|
GO:0044572
[4Fe-4S] cluster assembly
|
IMP
PMID:27532772 Mitochondrial Bol1 and Bol3 function as assembly factors for... |
NEW |
Summary: BOLA3 deficiency causes defects in [4Fe-4S] enzyme activities, demonstrating its role in [4Fe-4S] cluster assembly. The GLRX5-BOLA3 complex delivers [2Fe-2S] clusters to NFU1 for [4Fe-4S] assembly.
Reason: This is a more specific term than GO:0016226 (iron-sulfur cluster assembly) and accurately reflects BOLA3's role in the late ISC pathway for [4Fe-4S] protein maturation.
Supporting Evidence:
PMID:27532772
Deficiency of both mitochondrial Bol proteins causes defects in a subset of mitochondrial [4Fe-4S] enzymes
|
|
GO:1990229
iron-sulfur cluster assembly complex
|
IDA
PMID:27532772 Mitochondrial Bol1 and Bol3 function as assembly factors for... |
NEW |
Summary: BOLA3 is a component of the mitochondrial BOLA3-GLRX5 iron-sulfur cluster assembly complex (ComplexPortal:CPX-6863). This complex functions in Fe-S cluster transfer.
Reason: ComplexPortal has curated the BOLA3-GLRX5 complex and this annotation appropriately reflects BOLA3's participation in this assembly complex.
Supporting Evidence:
PMID:27532772
In order to characterize the interaction between BOLA1 or BOLA3 and GLRX5 at the atomic level
|
Q: What is the relative contribution of BOLA3 vs BOLA1 to different [4Fe-4S] client proteins? Uzarska et al. showed Bol1 and Bol3 have overlapping but distinct client specificities. Understanding this would help interpret MMDS2 pathophysiology.
Q: Does BOLA3 have functions independent of the GLRX5-BOLA3 heterocomplex? Some interactions detected in HTP studies may represent additional BOLA3 functions not yet characterized.
Experiment: Systematic identification of all BOLA3-dependent [4Fe-4S] client proteins using proteomics in BOLA3-deficient cells. This would provide comprehensive understanding of BOLA3's role in [4Fe-4S] protein maturation beyond known clients like LIAS and SDH.
Hypothesis: BOLA3 deficiency affects specific subset of mitochondrial [4Fe-4S] enzymes that can be comprehensively identified by proteomics.
Experiment: Structure determination of the BOLA3-GLRX5-[2Fe-2S]-NFU1 transfer complex. This would reveal mechanism of [2Fe-2S] cluster transfer from BOLA3-GLRX5 to NFU1 for [4Fe-4S] assembly.
Hypothesis: BOLA3-GLRX5 complex directly interacts with NFU1 during cluster transfer, forming a transient ternary complex.
provider: falcon
model: Edison Scientific Literature
cached: false
start_time: '2025-12-29T00:22:53.124350'
end_time: '2025-12-29T00:28:47.190758'
duration_seconds: 354.07
template_file: templates/gene_research_go_focused.md
template_variables:
organism: human
gene_id: BOLA3
gene_symbol: BOLA3
uniprot_accession: Q53S33
protein_description: 'RecName: Full=BolA-like protein 3 {ECO:0000305};'
gene_info: Name=BOLA3 {ECO:0000312|HGNC:HGNC:24415};
organism_full: Homo sapiens (Human).
protein_family: Belongs to the BolA/IbaG family. .
protein_domains: BolA. (IPR002634); BolA-like_sf. (IPR036065); Mt_Fe-S_assembly_factor.
(IPR052275); BolA (PF01722)
provider_config:
timeout: 600
max_retries: 3
parameters:
allowed_domains: []
temperature: 0.1
citation_count: 30
BEFORE YOU BEGIN RESEARCH: You MUST verify you are researching the CORRECT gene/protein. Gene symbols can be ambiguous, especially for less well-characterized genes from non-model organisms.
DO NOT PROCEED WITH RESEARCH ON A DIFFERENT GENE. Instead:
- State clearly: "The gene symbol 'BOLA3' is ambiguous or literature is limited for this specific protein"
- Explain what you found (e.g., "Found extensive literature on a different gene with the same symbol in a different organism")
- Describe the protein based ONLY on the UniProt information provided above
- Suggest that the protein function can be inferred from domain/family information
Please provide a comprehensive research report on the gene BOLA3 (gene ID: BOLA3, UniProt: Q53S33) in human.
The research report should be a detailed narrative explaining the function, biological processes, and localization of the gene product. Citations should be given for all claims.
You should prioritize authoritative reviews and primary scientific literature when conducting research. You can supplement
this with annotations you find in gene/protein databases, but these can be outdated or inaccurate.
We are specifically interested in the primary function of the gene - for enzymes, what reaction is catalyzed, and what is the substrate specificity? For transporters, what is the substrate? For structural proteins or adapters, what is the broader structural role? For signaling molecules, what is the role in the pathway.
We are interested in where in or outside the cell the gene product carries out its function.
We are also interested in the signaling or biochemical pathways in which the gene functions. We are less interested in broad pleiotropic effects, except where these elucidate the precise role.
Include evidence where possible. We are interested in both experimental evidence as well as inference from structure, evolution, or bioinformatic analysis. Precise studies should be prioritized over high-throughput, where available.
Question: You are an expert researcher providing comprehensive, well-cited information.
Provide detailed information focusing on:
1. Key concepts and definitions with current understanding
2. Recent developments and latest research (prioritize 2023-2024 sources)
3. Current applications and real-world implementations
4. Expert opinions and analysis from authoritative sources
5. Relevant statistics and data from recent studies
Format as a comprehensive research report with proper citations. Include URLs and publication dates where available.
Always prioritize recent, authoritative sources and provide specific citations for all major claims.
BEFORE YOU BEGIN RESEARCH: You MUST verify you are researching the CORRECT gene/protein. Gene symbols can be ambiguous, especially for less well-characterized genes from non-model organisms.
DO NOT PROCEED WITH RESEARCH ON A DIFFERENT GENE. Instead:
- State clearly: "The gene symbol 'BOLA3' is ambiguous or literature is limited for this specific protein"
- Explain what you found (e.g., "Found extensive literature on a different gene with the same symbol in a different organism")
- Describe the protein based ONLY on the UniProt information provided above
- Suggest that the protein function can be inferred from domain/family information
Please provide a comprehensive research report on the gene BOLA3 (gene ID: BOLA3, UniProt: Q53S33) in human.
The research report should be a detailed narrative explaining the function, biological processes, and localization of the gene product. Citations should be given for all claims.
You should prioritize authoritative reviews and primary scientific literature when conducting research. You can supplement
this with annotations you find in gene/protein databases, but these can be outdated or inaccurate.
We are specifically interested in the primary function of the gene - for enzymes, what reaction is catalyzed, and what is the substrate specificity? For transporters, what is the substrate? For structural proteins or adapters, what is the broader structural role? For signaling molecules, what is the role in the pathway.
We are interested in where in or outside the cell the gene product carries out its function.
We are also interested in the signaling or biochemical pathways in which the gene functions. We are less interested in broad pleiotropic effects, except where these elucidate the precise role.
Include evidence where possible. We are interested in both experimental evidence as well as inference from structure, evolution, or bioinformatic analysis. Precise studies should be prioritized over high-throughput, where available.
Research report: Human BOLA3 (UniProt Q53S33)
Plan and verification
- Verified identity: BOLA3 encodes human BolA-like protein 3, a member of the BolA/IbaG family with roles in mitochondrial iron–sulfur (Fe–S) protein biogenesis; recent biochemical and review literature discuss human BOLA3’s function and pathogenic variants, consistent with the UniProt entry (human; BolA family/domain) (bargagna2023understandingthemolecular pages 1-2, bargagna2024molecularpathwaysfor pages 40-44).
- Verified localization: BOLA3 functions within the mitochondrial Fe–S assembly (ISC) pathway, i.e., in mitochondria (zhong2023bola3andnfu1 pages 1-2, sheftel2012thehumanmitochondrial pages 1-2).
Key concepts and current definitions
- BOLA3 is a late-acting mitochondrial ISC accessory factor that partners with GLRX5 to form a heterocomplex bridged by a [2Fe–2S] cluster. In this complex, GLRX5 ligates via Cys67 and a glutathione cysteine, and BOLA3 contributes Cys59 and His96 ligands (human numbering). This complex acts as a [2Fe–2S] carrier/chaperone toward late ISC clients, notably NFU1 (bargagna2024molecularpathwaysfora pages 40-44, bargagna2024molecularpathwaysfor pages 40-44).
- Late ISC network architecture: the GLRX5–BOLA3 node supplies [2Fe–2S] clusters, whereas the ISCA1/ISCA2–IBA57 system and NFU1 are required to assemble and/or deliver [4Fe–4S] clusters to client proteins in mitochondria (zhong2023bola3andnfu1 pages 1-2, sheftel2012thehumanmitochondrial pages 1-2).
- Downstream processes: Proper BOLA3 function supports maturation of [4Fe–4S] enzymes, including lipoyl synthase (LIAS), thereby enabling protein lipoylation of pyruvate dehydrogenase (PDH), α‑ketoglutarate dehydrogenase (KGDH), and the glycine cleavage system H-protein; BOLA3 also contributes to mitochondrial respiratory complex activities and mitoribosomal Fe–S cluster insertion required for organellar translation (sheftel2012thehumanmitochondrial pages 1-2, zhong2023bola3andnfu1 pages 1-2, baker2014variantnonketotic pages 10-11).
Recent developments and latest research (emphasis 2023–2024)
- Mitoribosome Fe–S assembly: Zhong et al. demonstrated that human mitoribosomes contain three [2Fe–2S] clusters and receive them from the GLRX5–BOLA3 node; BOLA3 or NFU1 deficiency attenuates mitochondrial protein synthesis and contributes to the pathophysiology of MMDS (Multiple Mitochondrial Dysfunctions Syndromes). They also propose the ISCA1→NFU1 route inserts a [4Fe–4S] cluster into METTL17, a mitoribosome assembly factor (Nucleic Acids Research; advance access 12 Oct 2023; https://doi.org/10.1093/nar/gkad842) (zhong2023bola3andnfu1 pages 1-2).
- Variant-level mechanism for MMDS2: Bargagna et al. (2023 IJMS; 2024 review) dissected the pathogenic BOLA3 His96Arg (H96R) mutation. H96R preserves GLRX5 binding but produces an aberrant BOLA3–[2Fe–2S]–GLRX5 complex unable to transfer its cluster to NFU1 to assemble the NFU1 [4Fe–4S] cluster; this mechanistically explains the severe MMDS2 phenotype with impaired respiratory complexes and lipoylation defects. The review also catalogues BOLA3 variants, including Cys59Tyr (ligand site) with partial residual function (2023: https://doi.org/10.3390/ijms241411734) (bargagna2023understandingthemolecular pages 1-2, bargagna2024molecularpathwaysfor pages 55-56, bargagna2024molecularpathwaysfora pages 55-56, bargagna2023understandingthemolecular pages 11-12).
- Consolidation of late ISC roles: Earlier foundational work (Sheftel et al., 2012) established that ISCA1/ISCA2/IBA57 are required for mitochondrial [4Fe–4S] protein maturation and linked these factors to LIAS and lipoylation, a framework into which the GLRX5–BOLA3 node integrates (Mol Biol Cell; Apr 2012; https://doi.org/10.1091/mbc.e11-09-0772) (sheftel2012thehumanmitochondrial pages 1-2).
Current applications and real-world implementations
- Diagnostics: In variant nonketotic hyperglycinemia (vNKH) workups, sequencing of LIAS, BOLA3 and GLRX5 identifies etiologies; functional confirmation often uses western blot for lipoylated E2 subunits of PDH/KGDH and PDH enzyme assays. Baker et al. reported deficient protein lipoylation in 8/10 families and used complementation in fibroblasts to prove causality (Brain; Feb 2014; https://doi.org/10.1093/brain/awt328) (baker2014variantnonketotic pages 10-11, baker2014variantnonketotic pages 7-8, baker2014variantnonketotic pages 9-10).
- Mechanistic cell models: Zhong et al. used patient fibroblasts and gene knockdown to relate BOLA3/NFU1 deficiency to mitoribosome Fe–S cluster insertion and mitochondrial translation, now a platform for assessing pathogenic variants (zhong2023bola3andnfu1 pages 1-2).
- Gene/variant interpretation: Structural-biochemical assays (SEC, NMR, EPR, UV–vis/CD) of BOLA3 variants (H96R, C59Y) quantify effects on GLRX5 heterocomplex formation and NFU1 [4Fe–4S] assembly, informing pathogenicity classification (bargagna2023understandingthemolecular pages 1-2, bargagna2024molecularpathwaysfor pages 55-56, bargagna2024molecularpathwaysfora pages 55-56, bargagna2023understandingthemolecular pages 11-12).
Expert opinions and analyses from authoritative sources
- NAR 2023 (Zhong et al.) proposes a partitioned late ISC map: GLRX5–BOLA3 provides [2Fe–2S] to the mitoribosome, while ISCA1→NFU1 provides [4Fe–4S] to METTL17, arguing that impaired BOLA3 or NFU1 causes combined defects in electron transport chain enzymes and mitochondrial translation (zhong2023bola3andnfu1 pages 1-2).
- 2023–2024 expert reviews emphasize that BOLA3’s conserved His96 and Cys59 residues coordinate the [2Fe–2S] bridge within the GLRX5–BOLA3 complex, and that pathogenic substitution of these ligands explains loss of downstream [4Fe–4S] maturation and lipoylation (bargagna2024molecularpathwaysfora pages 40-44, bargagna2024molecularpathwaysfor pages 55-56, bargagna2024molecularpathwaysfor pages 40-44).
Relevant statistics and recent clinical data
- Variant NKH cohort: Baker et al. studied 11 patients from 10 families; genetic etiologies were defined for 8 patients with mutations in LIAS, BOLA3, or GLRX5. In that series, protein lipoylation defects were shown in 8 of 10 families tested (Brain; 2014) (baker2014variantnonketotic pages 2-3, baker2014variantnonketotic pages 10-11).
- BOLA3 clinical course: BOLA3-associated vNKH/MMDS2 is typically infantile and often fatal in the first year of life; recurrent truncating BOLA3 variant c.136C>T (p.R46X) occurred homozygously in multiple families (baker2014variantnonketotic pages 2-3, baker2014variantnonketotic pages 7-8).
- GLRX5 context for the node: A 2024 case report of GLRX5-mediated NKH presented with early-onset severe disease and death by ~4 months, underscoring the GLRX5–BOLA3–LIAS functional axis in lipoylation and glycine cleavage (Frontiers in Genetics; Sep 2024; https://doi.org/10.3389/fgene.2024.1432272) (marin2024casereportunveiling pages 3-4).
Mechanistic pathway synthesis
- Early ISC steps produce [2Fe–2S] clusters that are transferred to GLRX5. The GLRX5–BOLA3 heterocomplex binds a bridged [2Fe–2S] cluster via GLRX5 Cys67/glutathione and BOLA3 Cys59/His96, forming a mobile chaperone unit. Two such [2Fe–2S] equivalents can be delivered to NFU1, where reductive coupling yields a [4Fe–4S] cluster for late clients including LIAS and additional [4Fe–4S] assembly factors; in parallel, ISCA1/ISCA2/IBA57 function in [4Fe–4S] biogenesis/delivery, and GLRX5–BOLA3 supplies [2Fe–2S] to the mitoribosome (bargagna2024molecularpathwaysfora pages 40-44, bargagna2024molecularpathwaysfor pages 40-44, zhong2023bola3andnfu1 pages 1-2, sheftel2012thehumanmitochondrial pages 1-2).
- Pathogenic H96R disrupts BOLA3’s histidine ligand, generating an aberrant GLRX5–BOLA3 complex that cannot complete [2Fe–2S] → [4Fe–4S] transfer on NFU1, mechanistically explaining combined defects in respiratory complexes and lipoylation (bargagna2023understandingthemolecular pages 1-2, bargagna2023understandingthemolecular pages 11-12). C59Y produces partial loss consistent with milder phenotypes (bargagna2024molecularpathwaysfora pages 55-56).
Clinical phenotypes and disease links
- Multiple Mitochondrial Dysfunctions Syndrome type 2 (MMDS2): Biallelic BOLA3 variants cause leukodystrophy/encephalopathy with lactic acidosis and hyperglycinemia; biochemical findings include reduced activities of respiratory complexes and decreased activity of lipoyl-dependent enzymes (PDH, KGDH, glycine cleavage H-protein). Infantile lethality is common (bargagna2023understandingthemolecular pages 1-2, baker2014variantnonketotic pages 2-3).
- Variant nonketotic hyperglycinemia (vNKH): Mutations in LIAS, BOLA3, or GLRX5 lead to vNKH characterized by elevated plasma (and milder CSF) glycine and defective protein lipoylation; diagnostic lipoylation blotting was abnormal in most studied families (baker2014variantnonketotic pages 10-11, baker2014variantnonketotic pages 3-3, baker2014variantnonketotic pages 11-12).
URLs and publication dates (where available)
- Zhong et al., Nucleic Acids Research, advance access 12 Oct 2023: https://doi.org/10.1093/nar/gkad842 (zhong2023bola3andnfu1 pages 1-2).
- Bargagna et al., IJMS, 21 Jul 2023: https://doi.org/10.3390/ijms241411734 (bargagna2023understandingthemolecular pages 1-2).
- Sheftel et al., Mol Biol Cell, Apr 2012: https://doi.org/10.1091/mbc.e11-09-0772 (sheftel2012thehumanmitochondrial pages 1-2).
- Baker et al., Brain, Feb 2014: https://doi.org/10.1093/brain/awt328 (baker2014variantnonketotic pages 10-11, baker2014variantnonketotic pages 2-3, baker2014variantnonketotic pages 7-8, baker2014variantnonketotic pages 9-10, baker2014variantnonketotic pages 11-11, baker2014variantnonketotic pages 11-12, baker2014variantnonketotic pages 3-3).
- Marin et al., Frontiers in Genetics, Sep 2024: https://doi.org/10.3389/fgene.2024.1432272 (marin2024casereportunveiling pages 3-4).
Embedded summary table
| Category | Key points (compact) | Evidence |
|---|---|---|
| Identity / verification | Human gene BOLA3 (UniProt Q53S33). Member of BolA family with BolA/BolA-like and Mt_Fe-S_assembly_factor domains (BolA, BolA-like_sf, IPR052275). | (bargagna2023understandingthemolecular pages 1-2, bargagna2024molecularpathwaysfor pages 40-44) |
| Cellular localization | Mitochondrial matrix/mitochondrial ISC system (mitochondrial targeting; functions in mitochondrial Fe–S biogenesis). | (zhong2023bola3andnfu1 pages 1-2, sheftel2012thehumanmitochondrial pages 1-2) |
| Mechanistic role & primary interactors | Forms a heterocomplex with mitochondrial GLRX5 that binds a bridged [2Fe-2S] cluster; functions as a late-acting ISC accessory/chaperone delivering cluster equivalents toward NFU1 and clients. Interacts functionally with NFU1; works in network with ISCA1/2 and IBA57. | (bargagna2023understandingthemolecular pages 1-2, bargagna2024molecularpathwaysfor pages 40-44, zhong2023bola3andnfu1 pages 1-2, sheftel2012thehumanmitochondrial pages 1-2) |
| ISC pathway nodes (who supplies which) | GLRX5–BOLA3 node: supplies/hosts [2Fe-2S] bridged clusters (donor node). ISCA1/2–IBA57 (and ISCA1/2→NFU1) route: late [4Fe-4S] assembly/delivery to mitochondrial clients; NFU1 receives/converts two [2Fe-2S] inputs to a [4Fe-4S] on NFU1. | (zhong2023bola3andnfu1 pages 1-2, bargagna2023understandingthemolecular pages 1-2, sheftel2012thehumanmitochondrial pages 1-2) |
| Downstream processes affected | LIAS (lipoyl synthase) maturation and protein lipoylation (PDH, KGDH, GCS H-protein), respiratory complex activities, and mitoribosome [2Fe-2S] insertion/assembly → impacts mitochondrial protein synthesis. | (sheftel2012thehumanmitochondrial pages 1-2, zhong2023bola3andnfu1 pages 1-2, baker2014variantnonketotic pages 10-11) |
| Key 2023–2024 advances | 2023: Zhong et al. linked GLRX5–BOLA3 node to mitoribosomal [2Fe-2S] clusters and showed BOLA3/NFU1 loss attenuates mitochondrial translation (mitoribosome stability) (zhong2023bola3andnfu1 pages 1-2). 2023–2024: Bargagna et al. biochemical/structural dissection of H96R and C59Y variants showed H96R forms aberrant GLRX5–BOLA3 heterocomplex that cannot assemble [4Fe-4S] on NFU1 (mechanistic basis for MMDS2); reviews (2024) consolidate late-ISC pathway roles. | (zhong2023bola3andnfu1 pages 1-2, bargagna2023understandingthemolecular pages 1-2, bargagna2024molecularpathwaysfor pages 40-44, bargagna2024molecularpathwaysfor pages 55-56) |
| Disease links & clinical phenotype | Biallelic BOLA3 mutations → MMDS2 (multiple mitochondrial dysfunctions syndrome type 2): leukodystrophy/encephalopathy, lactic acidosis, hyperglycinemia, early lethal neonatal/infantile course. BOLA3 (with LIAS, GLRX5) implicated in variant non‑ketotic hyperglycinemia (vNKH) with lipoylation defects. | (bargagna2023understandingthemolecular pages 1-2, baker2014variantnonketotic pages 10-11, baker2014variantnonketotic pages 2-3) |
| Variants (functional effects) & selected statistics | Functionally characterized: H96R (c.287A>G) — preserves GLRX5 binding but yields nonfunctional BOLA3–[2Fe-2S]–GLRX5 unable to transfer/assemble [4Fe-4S] on NFU1; associated with severe MMDS2 and death in infancy (reported fatal <1 yr) (bargagna2023understandingthemolecular pages 1-2, bargagna2023understandingthemolecular pages 11-12). C59Y — perturbs cluster ligand, retains partial activity → milder phenotype (bargagna2024molecularpathwaysfor pages 40-44). R46X (c.136C>T) recurrent truncation seen homozygous in multiple families (baker2014variantnonketotic pages 7-8). Reported counts: Baker et al. cohort = 11 patients (10 families) with vNKH; genetic diagnosis in 8/11 (LIAS, BOLA3, GLRX5) and several pathogenic BOLA3 alleles reported (~8 described in literature excerpt). Typical BOLA3 cases often fatal in first year (cohort-level note). | (bargagna2023understandingthemolecular pages 11-12, bargagna2024molecularpathwaysfor pages 40-44, baker2014variantnonketotic pages 7-8, baker2014variantnonketotic pages 2-3, baker2014variantnonketotic pages 9-10) |
Table: Compact summary table of human BOLA3 (Q53S33) covering identity, localization, mechanistic role in Fe–S biogenesis, downstream processes, 2023–2024 advances, disease links, key variants and available cohort statistics with primary evidence citations.
Conclusion
Human BOLA3 is a mitochondrial BolA-family factor that forms a [2Fe–2S]-bridged heterocomplex with GLRX5, acting at a late ISC node to support NFU1-dependent [4Fe–4S] maturation, lipoyl synthase function and mitoribosomal Fe–S insertion. 2023–2024 work clarified that GLRX5–BOLA3 supplies mitoribosomal [2Fe–2S] clusters and that specific BOLA3 ligand-site variants (H96R, C59Y) explain MMDS2 mechanistically. Clinically, BOLA3 deficiency underlies MMDS2 and contributes to variant NKH with characteristic lipoylation defects, often with infantile lethality. These insights guide molecular diagnostics (sequencing of LIAS/BOLA3/GLRX5; lipoylation assays) and functional variant assessment strategies (zhong2023bola3andnfu1 pages 1-2, bargagna2023understandingthemolecular pages 1-2, baker2014variantnonketotic pages 10-11).
References
(bargagna2023understandingthemolecular pages 1-2): Beatrice Bargagna, Lucia Banci, and Francesca Camponeschi. Understanding the molecular basis of the multiple mitochondrial dysfunctions syndrome 2: the disease-causing his96arg mutation of bola3. International Journal of Molecular Sciences, 24:11734, Jul 2023. URL: https://doi.org/10.3390/ijms241411734, doi:10.3390/ijms241411734. This article has 1 citations and is from a poor quality or predatory journal.
(bargagna2024molecularpathwaysfor pages 40-44): B Bargagna. Molecular pathways for the maturation of mitochondrial and cytosolic human fe-s proteins. Unknown journal, 2024.
(zhong2023bola3andnfu1 pages 1-2): Hui Zhong, Alexandre Janer, Oleh Khalimonchuk, Hana Antonicka, Eric A Shoubridge, and Antoni Barrientos. Bola3 and nfu1 link mitoribosome iron–sulfur cluster assembly to multiple mitochondrial dysfunctions syndrome. Nucleic Acids Research, 51:11797-11812, Oct 2023. URL: https://doi.org/10.1093/nar/gkad842, doi:10.1093/nar/gkad842. This article has 31 citations and is from a highest quality peer-reviewed journal.
(sheftel2012thehumanmitochondrial pages 1-2): Alex D. Sheftel, Claudia Wilbrecht, Oliver Stehling, Brigitte Niggemeyer, Hans-Peter Elsässer, Ulrich Mühlenhoff, and Roland Lill. The human mitochondrial isca1, isca2, and iba57 proteins are required for [4fe-4s] protein maturation. Molecular Biology of the Cell, 23:1157-1166, Apr 2012. URL: https://doi.org/10.1091/mbc.e11-09-0772, doi:10.1091/mbc.e11-09-0772. This article has 250 citations and is from a domain leading peer-reviewed journal.
(bargagna2024molecularpathwaysfora pages 40-44): B Bargagna. Molecular pathways for the maturation of mitochondrial and cytosolic human fe-s proteins. Unknown journal, 2024.
(baker2014variantnonketotic pages 10-11): Peter R. Baker, Marisa W. Friederich, Michael A. Swanson, Tamim Shaikh, Kaustuv Bhattacharya, Gunter H. Scharer, Joseph Aicher, Geralyn Creadon-Swindell, Elizabeth Geiger, Kenneth N. MacLean, Wang-Tso Lee, Charu Deshpande, Mary-Louise Freckmann, Ling-Yu Shih, Melissa Wasserstein, Malene B. Rasmussen, Allan M. Lund, Peter Procopis, Jessie M. Cameron, Brian H. Robinson, Garry K. Brown, Ruth M. Brown, Alison G. Compton, Carol L. Dieckmann, Renata Collard, Curtis R. Coughlin, Elaine Spector, Michael F. Wempe, and Johan L.K. Van Hove. Variant non ketotic hyperglycinemia is caused by mutations in lias, bola3 and the novel gene glrx5. Brain : a journal of neurology, 137 Pt 2:366-79, Feb 2014. URL: https://doi.org/10.1093/brain/awt328, doi:10.1093/brain/awt328. This article has 258 citations.
(bargagna2024molecularpathwaysfor pages 55-56): B Bargagna. Molecular pathways for the maturation of mitochondrial and cytosolic human fe-s proteins. Unknown journal, 2024.
(bargagna2024molecularpathwaysfora pages 55-56): B Bargagna. Molecular pathways for the maturation of mitochondrial and cytosolic human fe-s proteins. Unknown journal, 2024.
(bargagna2023understandingthemolecular pages 11-12): Beatrice Bargagna, Lucia Banci, and Francesca Camponeschi. Understanding the molecular basis of the multiple mitochondrial dysfunctions syndrome 2: the disease-causing his96arg mutation of bola3. International Journal of Molecular Sciences, 24:11734, Jul 2023. URL: https://doi.org/10.3390/ijms241411734, doi:10.3390/ijms241411734. This article has 1 citations and is from a poor quality or predatory journal.
(baker2014variantnonketotic pages 7-8): Peter R. Baker, Marisa W. Friederich, Michael A. Swanson, Tamim Shaikh, Kaustuv Bhattacharya, Gunter H. Scharer, Joseph Aicher, Geralyn Creadon-Swindell, Elizabeth Geiger, Kenneth N. MacLean, Wang-Tso Lee, Charu Deshpande, Mary-Louise Freckmann, Ling-Yu Shih, Melissa Wasserstein, Malene B. Rasmussen, Allan M. Lund, Peter Procopis, Jessie M. Cameron, Brian H. Robinson, Garry K. Brown, Ruth M. Brown, Alison G. Compton, Carol L. Dieckmann, Renata Collard, Curtis R. Coughlin, Elaine Spector, Michael F. Wempe, and Johan L.K. Van Hove. Variant non ketotic hyperglycinemia is caused by mutations in lias, bola3 and the novel gene glrx5. Brain : a journal of neurology, 137 Pt 2:366-79, Feb 2014. URL: https://doi.org/10.1093/brain/awt328, doi:10.1093/brain/awt328. This article has 258 citations.
(baker2014variantnonketotic pages 9-10): Peter R. Baker, Marisa W. Friederich, Michael A. Swanson, Tamim Shaikh, Kaustuv Bhattacharya, Gunter H. Scharer, Joseph Aicher, Geralyn Creadon-Swindell, Elizabeth Geiger, Kenneth N. MacLean, Wang-Tso Lee, Charu Deshpande, Mary-Louise Freckmann, Ling-Yu Shih, Melissa Wasserstein, Malene B. Rasmussen, Allan M. Lund, Peter Procopis, Jessie M. Cameron, Brian H. Robinson, Garry K. Brown, Ruth M. Brown, Alison G. Compton, Carol L. Dieckmann, Renata Collard, Curtis R. Coughlin, Elaine Spector, Michael F. Wempe, and Johan L.K. Van Hove. Variant non ketotic hyperglycinemia is caused by mutations in lias, bola3 and the novel gene glrx5. Brain : a journal of neurology, 137 Pt 2:366-79, Feb 2014. URL: https://doi.org/10.1093/brain/awt328, doi:10.1093/brain/awt328. This article has 258 citations.
(baker2014variantnonketotic pages 2-3): Peter R. Baker, Marisa W. Friederich, Michael A. Swanson, Tamim Shaikh, Kaustuv Bhattacharya, Gunter H. Scharer, Joseph Aicher, Geralyn Creadon-Swindell, Elizabeth Geiger, Kenneth N. MacLean, Wang-Tso Lee, Charu Deshpande, Mary-Louise Freckmann, Ling-Yu Shih, Melissa Wasserstein, Malene B. Rasmussen, Allan M. Lund, Peter Procopis, Jessie M. Cameron, Brian H. Robinson, Garry K. Brown, Ruth M. Brown, Alison G. Compton, Carol L. Dieckmann, Renata Collard, Curtis R. Coughlin, Elaine Spector, Michael F. Wempe, and Johan L.K. Van Hove. Variant non ketotic hyperglycinemia is caused by mutations in lias, bola3 and the novel gene glrx5. Brain : a journal of neurology, 137 Pt 2:366-79, Feb 2014. URL: https://doi.org/10.1093/brain/awt328, doi:10.1093/brain/awt328. This article has 258 citations.
(marin2024casereportunveiling pages 3-4): Victor Marin, Louis Lebreton, Claire Guibet, Samir Mesli, Isabelle Redonnet-Vernhet, Mathurin Dexant, Delphine Lamireau, Sandrine Roche, Margaux Gaschignard, Jean Delmas, Henri Margot, and Claire Bar. Case report: unveiling genetic and phenotypic variability in nonketotic hyperglycinemia: an atypical early onset case associated with a novel glrx5 variant. Frontiers in Genetics, Sep 2024. URL: https://doi.org/10.3389/fgene.2024.1432272, doi:10.3389/fgene.2024.1432272. This article has 1 citations and is from a peer-reviewed journal.
(baker2014variantnonketotic pages 3-3): Peter R. Baker, Marisa W. Friederich, Michael A. Swanson, Tamim Shaikh, Kaustuv Bhattacharya, Gunter H. Scharer, Joseph Aicher, Geralyn Creadon-Swindell, Elizabeth Geiger, Kenneth N. MacLean, Wang-Tso Lee, Charu Deshpande, Mary-Louise Freckmann, Ling-Yu Shih, Melissa Wasserstein, Malene B. Rasmussen, Allan M. Lund, Peter Procopis, Jessie M. Cameron, Brian H. Robinson, Garry K. Brown, Ruth M. Brown, Alison G. Compton, Carol L. Dieckmann, Renata Collard, Curtis R. Coughlin, Elaine Spector, Michael F. Wempe, and Johan L.K. Van Hove. Variant non ketotic hyperglycinemia is caused by mutations in lias, bola3 and the novel gene glrx5. Brain : a journal of neurology, 137 Pt 2:366-79, Feb 2014. URL: https://doi.org/10.1093/brain/awt328, doi:10.1093/brain/awt328. This article has 258 citations.
(baker2014variantnonketotic pages 11-12): Peter R. Baker, Marisa W. Friederich, Michael A. Swanson, Tamim Shaikh, Kaustuv Bhattacharya, Gunter H. Scharer, Joseph Aicher, Geralyn Creadon-Swindell, Elizabeth Geiger, Kenneth N. MacLean, Wang-Tso Lee, Charu Deshpande, Mary-Louise Freckmann, Ling-Yu Shih, Melissa Wasserstein, Malene B. Rasmussen, Allan M. Lund, Peter Procopis, Jessie M. Cameron, Brian H. Robinson, Garry K. Brown, Ruth M. Brown, Alison G. Compton, Carol L. Dieckmann, Renata Collard, Curtis R. Coughlin, Elaine Spector, Michael F. Wempe, and Johan L.K. Van Hove. Variant non ketotic hyperglycinemia is caused by mutations in lias, bola3 and the novel gene glrx5. Brain : a journal of neurology, 137 Pt 2:366-79, Feb 2014. URL: https://doi.org/10.1093/brain/awt328, doi:10.1093/brain/awt328. This article has 258 citations.
(baker2014variantnonketotic pages 11-11): Peter R. Baker, Marisa W. Friederich, Michael A. Swanson, Tamim Shaikh, Kaustuv Bhattacharya, Gunter H. Scharer, Joseph Aicher, Geralyn Creadon-Swindell, Elizabeth Geiger, Kenneth N. MacLean, Wang-Tso Lee, Charu Deshpande, Mary-Louise Freckmann, Ling-Yu Shih, Melissa Wasserstein, Malene B. Rasmussen, Allan M. Lund, Peter Procopis, Jessie M. Cameron, Brian H. Robinson, Garry K. Brown, Ruth M. Brown, Alison G. Compton, Carol L. Dieckmann, Renata Collard, Curtis R. Coughlin, Elaine Spector, Michael F. Wempe, and Johan L.K. Van Hove. Variant non ketotic hyperglycinemia is caused by mutations in lias, bola3 and the novel gene glrx5. Brain : a journal of neurology, 137 Pt 2:366-79, Feb 2014. URL: https://doi.org/10.1093/brain/awt328, doi:10.1093/brain/awt328. This article has 258 citations.
id: Q53S33
gene_symbol: BOLA3
product_type: PROTEIN
status: COMPLETE
taxon:
id: NCBITaxon:9606
label: Homo sapiens
description: BOLA3 is a mitochondrial BolA-family protein that functions as a
late-acting iron-sulfur (Fe-S) cluster assembly factor. BOLA3 forms a
heterocomplex with the mitochondrial monothiol glutaredoxin GLRX5, bridged by
a [2Fe-2S] cluster (coordinated by BOLA3 Cys59 and His96, and GLRX5 Cys67 plus
glutathione). This GLRX5-BOLA3 complex acts as a [2Fe-2S] carrier/chaperone
that delivers cluster equivalents to NFU1, where two [2Fe-2S] clusters are
converted to a [4Fe-4S] cluster for insertion into downstream client proteins
including lipoyl synthase (LIAS), succinate dehydrogenase, and the
mitoribosome. BOLA3 deficiency causes Multiple Mitochondrial Dysfunctions
Syndrome type 2 (MMDS2), characterized by defective protein lipoylation,
impaired respiratory chain complex activities, and attenuated mitochondrial
translation.
existing_annotations:
- term:
id: GO:0051604
label: protein maturation
evidence_type: IBA
original_reference_id: GO_REF:0000033
review:
summary: This annotation captures BOLA3's role in facilitating Fe-S
cluster insertion into mitochondrial proteins, which is a form of
protein maturation. BOLA3 functions in the late ISC pathway to enable
[4Fe-4S] protein maturation (PMID:27532772).
action: MODIFY
reason: While "protein maturation" is technically accurate, it is too
general. BOLA3 specifically functions in iron-sulfur cluster assembly
and insertion. More precise terms exist that better describe the
molecular function.
proposed_replacement_terms:
- id: GO:0016226
label: iron-sulfur cluster assembly
- id: GO:0044572
label: '[4Fe-4S] cluster assembly'
supported_by:
- reference_id: PMID:27532772
supporting_text: Bol1 and Bol3 as specific mitochondrial ISC assembly
factors that facilitate [4Fe-4S] cluster insertion into a subset of
mitochondrial proteins such as lipoate synthase and succinate
dehydrogenase
- reference_id: file:human/BOLA3/BOLA3-deep-research-falcon.md
supporting_text: 'model: Edison Scientific Literature'
- term:
id: GO:0005759
label: mitochondrial matrix
evidence_type: IBA
original_reference_id: GO_REF:0000033
review:
summary: BOLA3 localizes to mitochondria where it functions in the
mitochondrial ISC assembly pathway. Multiple lines of evidence support
mitochondrial localization (PMID:22746225, PMID:27532772).
action: ACCEPT
reason: The mitochondrial matrix localization is well-supported by
phylogenetic inference (IBA) and is consistent with experimental data.
BOLA3 functions within the mitochondrial ISC pathway alongside GLRX5 and
NFU1.
supported_by:
- reference_id: PMID:22746225
supporting_text: BOLA1 is a mitochondrial protein
- reference_id: PMID:27532772
supporting_text: Mitochondrial Bol1 and Bol3 function as assembly
factors for specific iron-sulfur proteins
- term:
id: GO:0005739
label: mitochondrion
evidence_type: IEA
original_reference_id: GO_REF:0000120
review:
summary: Automated annotation of mitochondrial localization is correct and
consistent with experimental data showing BOLA3 is a mitochondrial
protein (PMID:22746225).
action: ACCEPT
reason: This IEA annotation is broader than the IBA to mitochondrial
matrix but is not incorrect. Multiple annotations at different
specificity levels are acceptable.
supported_by:
- reference_id: PMID:22746225
supporting_text: We show that BOLA1 is a mitochondrial protein
- term:
id: GO:0005515
label: protein binding
evidence_type: IPI
original_reference_id: PMID:27499296
review:
summary: This annotation captures interaction with GLRX5 from a
mitochondrial protein interaction mapping study. The interaction is
functionally significant.
action: MODIFY
reason: '"Protein binding" is too vague and uninformative. BOLA3 specifically
binds GLRX5 to form a Fe-S cluster-bridged heterocomplex. A more informative
MF term should be used.'
proposed_replacement_terms:
- id: GO:0051537
label: 2 iron, 2 sulfur cluster binding
supported_by:
- reference_id: PMID:27532772
supporting_text: BOLA1 or BOLA3 and GLRX5 at the atomic level
- reference_id: PMID:27499296
supporting_text: 2016 Aug 4. Mitochondrial Protein Interaction Mapping
Identifies Regulators of Respiratory Chain Function.
- term:
id: GO:0005515
label: protein binding
evidence_type: IPI
original_reference_id: PMID:27532772
review:
summary: This annotation reflects the physical interaction between BOLA3
and GLRX5 demonstrated by NMR spectroscopy. BOLA3 forms a
[2Fe-2S]-bridged heterocomplex with GLRX5, with BOLA3 Cys59 and His96
serving as cluster ligands (PMID:27532772).
action: MODIFY
reason: '"Protein binding" does not capture the specific nature of the BOLA3-GLRX5
interaction. The interaction involves forming a Fe-S cluster-bridged complex
essential for cluster transfer.'
proposed_replacement_terms:
- id: GO:0051537
label: 2 iron, 2 sulfur cluster binding
supported_by:
- reference_id: PMID:27532772
supporting_text: The structures of (A) BOLA1 and (B) BOLA3 were solved
by solution NMR. Residues His58, His67 and His102 are conserved
within the eukaryotic BOLA1 proteins, and residues Cys59 and His96
are conserved within the BOLA3 proteins
- term:
id: GO:0005515
label: protein binding
evidence_type: IPI
original_reference_id: PMID:32296183
review:
summary: High-throughput binary interactome mapping study. The specific
interaction partners from this study include GLRX5.
action: MARK_AS_OVER_ANNOTATED
reason: Generic "protein binding" from HTP studies provides limited
functional insight. The functionally relevant interactions (GLRX5, NFU1)
are better captured through more specific annotations.
supported_by:
- reference_id: PMID:32296183
supporting_text: Apr 8. A reference map of the human binary protein
interactome.
- term:
id: GO:0005515
label: protein binding
evidence_type: IPI
original_reference_id: PMID:33961781
review:
summary: Dual proteome-scale interactome study. This is a high-throughput
study.
action: MARK_AS_OVER_ANNOTATED
reason: Generic "protein binding" from HTP proteome-scale studies is not
informative for functional annotation. The core BOLA3-GLRX5 interaction
is better captured with more specific terms.
supported_by:
- reference_id: PMID:33961781
supporting_text: 2021 May 6. Dual proteome-scale networks reveal
cell-specific remodeling of the human interactome.
- term:
id: GO:0005515
label: protein binding
evidence_type: IPI
original_reference_id: PMID:34063696
review:
summary: This study examined the C59Y BOLA3 variant and demonstrated that
the mutant still forms a heterocomplex with GLRX5, though with altered
properties. The interaction between BOLA3 and GLRX5 involves [2Fe-2S]
cluster coordination.
action: MODIFY
reason: The study provides detailed molecular characterization of the
BOLA3-GLRX5 interaction showing cluster binding. More specific terms
should be used.
proposed_replacement_terms:
- id: GO:0051537
label: 2 iron, 2 sulfur cluster binding
supported_by:
- reference_id: PMID:34063696
supporting_text: C59Y BOLA3-GLRX5 Complex Bound a [2Fe-2S]2+ Cluster
- term:
id: GO:0005739
label: mitochondrion
evidence_type: IDA
original_reference_id: GO_REF:0000052
review:
summary: HPA immunofluorescence data supporting mitochondrial
localization.
action: ACCEPT
reason: Direct experimental evidence for mitochondrial localization is
consistent with the known function of BOLA3 in the mitochondrial ISC
assembly pathway.
supported_by: []
- term:
id: GO:0005739
label: mitochondrion
evidence_type: NAS
original_reference_id: PMID:22746225
review:
summary: This study primarily characterized BOLA1 but also demonstrated
that the BolA family proteins are mitochondrial. BOLA3 was mentioned in
the context of mitochondrial Fe-S cluster biogenesis.
action: ACCEPT
reason: The study provides supporting evidence for mitochondrial
localization of the BolA family proteins, consistent with their role in
mitochondrial ISC assembly.
supported_by:
- reference_id: PMID:22746225
supporting_text: BOLA3 has recently been implicated in the biogenesis
of [Fe-S] clusters for oxidative phosphorylation complexes and 2-oxo
acid dehydrogenase enzymes in mitochondria
- term:
id: GO:0006879
label: intracellular iron ion homeostasis
evidence_type: NAS
original_reference_id: PMID:27532772
review:
summary: The BOLA3-GLRX5 complex functions in Fe-S cluster assembly, which
indirectly affects iron homeostasis. However, BOLA3's primary role is in
Fe-S cluster biogenesis rather than direct iron sensing or trafficking.
action: KEEP_AS_NON_CORE
reason: While BOLA3 does influence iron homeostasis through its role in
Fe-S cluster assembly, this is a downstream consequence rather than the
core function. The primary role is in [4Fe-4S] cluster assembly.
supported_by:
- reference_id: PMID:27532772
supporting_text: Bol1 and Bol3 as specific mitochondrial ISC assembly
factors
- term:
id: GO:0016226
label: iron-sulfur cluster assembly
evidence_type: NAS
original_reference_id: PMID:27532772
review:
summary: BOLA3 functions in the late phase of mitochondrial Fe-S cluster
assembly, specifically facilitating [4Fe-4S] cluster insertion into
target proteins. The GLRX5-BOLA3 complex delivers [2Fe-2S] clusters to
NFU1 for [4Fe-4S] assembly (PMID:27532772).
action: ACCEPT
reason: This is a core function annotation. BOLA3 is a bona fide Fe-S
cluster assembly factor as demonstrated by biochemical and genetic
studies. The NAS evidence appropriately reflects the complex molecular
pathway.
supported_by:
- reference_id: PMID:27532772
supporting_text: we characterize the BOLA family proteins Bol1 and
Bol3 as specific mitochondrial ISC assembly factors that facilitate
[4Fe-4S] cluster insertion into a subset of mitochondrial proteins
such as lipoate synthase and succinate dehydrogenase
- term:
id: GO:0045454
label: cell redox homeostasis
evidence_type: NAS
original_reference_id: PMID:27532772
review:
summary: BolA proteins interact with glutaredoxins and have been
implicated in redox regulation. However, the primary characterized
function of BOLA3 is in Fe-S cluster assembly rather than direct redox
regulation.
action: KEEP_AS_NON_CORE
reason: This annotation likely reflects the association with GLRX5, a
glutaredoxin. While the BOLA3-GLRX5 interaction is functionally
important, the primary role is in Fe-S cluster transfer rather than
redox homeostasis per se.
supported_by:
- reference_id: PMID:22746225
supporting_text: A measured interaction of BOLA1 with the
mitochondrial monothiol glutaredoxin GLRX5 provides hints for
potential mechanisms behind BOLA1's effect on mitochondrial redox
potential
- reference_id: PMID:27532772
supporting_text: Mitochondrial Bol1 and Bol3 function as assembly
factors for specific iron-sulfur proteins.
- term:
id: GO:0005739
label: mitochondrion
evidence_type: HTP
original_reference_id: PMID:34800366
review:
summary: High-confidence human mitochondrial proteome study confirms
mitochondrial localization.
action: ACCEPT
reason: HTP proteomics evidence is consistent with other evidence for
mitochondrial localization of BOLA3.
supported_by:
- reference_id: PMID:34800366
supporting_text: Epub 2021 Nov 19. Quantitative high-confidence human
mitochondrial proteome and its dynamics in cellular context.
- term:
id: GO:0005739
label: mitochondrion
evidence_type: IDA
original_reference_id: PMID:22746225
review:
summary: Direct experimental evidence from the Willems et al. study that
characterized BolA family proteins as mitochondrial.
action: ACCEPT
reason: IDA evidence for mitochondrial localization is well-supported and
consistent with BOLA3's role in the mitochondrial ISC pathway.
supported_by:
- reference_id: PMID:22746225
supporting_text: BOLA1 is a mitochondrial protein
- term:
id: GO:0051537
label: 2 iron, 2 sulfur cluster binding
evidence_type: IDA
original_reference_id: PMID:27532772
review:
summary: BOLA3 binds a [2Fe-2S] cluster as part of the GLRX5-BOLA3
heterocomplex. NMR and spectroscopic studies demonstrate that BOLA3
Cys59 and His96 serve as cluster ligands (PMID:27532772, PMID:34063696).
action: NEW
reason: This is a core molecular function that is well-characterized but
not present in the current annotation set. The [2Fe-2S] cluster binding
is essential for BOLA3's function as a cluster carrier.
supported_by:
- reference_id: PMID:27532772
supporting_text: residues Cys59 and His96 are conserved within the
BOLA3 proteins
- reference_id: PMID:34063696
supporting_text: C59Y BOLA3-GLRX5 Complex Bound a [2Fe-2S]2+ Cluster
- term:
id: GO:0044572
label: '[4Fe-4S] cluster assembly'
evidence_type: IMP
original_reference_id: PMID:27532772
review:
summary: BOLA3 deficiency causes defects in [4Fe-4S] enzyme activities,
demonstrating its role in [4Fe-4S] cluster assembly. The GLRX5-BOLA3
complex delivers [2Fe-2S] clusters to NFU1 for [4Fe-4S] assembly.
action: NEW
reason: This is a more specific term than GO:0016226 (iron-sulfur cluster
assembly) and accurately reflects BOLA3's role in the late ISC pathway
for [4Fe-4S] protein maturation.
supported_by:
- reference_id: PMID:27532772
supporting_text: Deficiency of both mitochondrial Bol proteins causes
defects in a subset of mitochondrial [4Fe-4S] enzymes
- term:
id: GO:1990229
label: iron-sulfur cluster assembly complex
evidence_type: IDA
original_reference_id: PMID:27532772
review:
summary: BOLA3 is a component of the mitochondrial BOLA3-GLRX5 iron-sulfur
cluster assembly complex (ComplexPortal:CPX-6863). This complex
functions in Fe-S cluster transfer.
action: NEW
reason: ComplexPortal has curated the BOLA3-GLRX5 complex and this
annotation appropriately reflects BOLA3's participation in this assembly
complex.
supported_by:
- reference_id: PMID:27532772
supporting_text: In order to characterize the interaction between
BOLA1 or BOLA3 and GLRX5 at the atomic level
references:
- id: GO_REF:0000033
title: Annotation inferences using phylogenetic trees
findings:
- statement: BOLA3 annotated based on phylogenetic inference from yeast
orthologs
- id: GO_REF:0000052
title: Gene Ontology annotation based on curation of immunofluorescence data
findings: []
- id: GO_REF:0000120
title: Combined Automated Annotation using Multiple IEA Methods
findings: []
- id: PMID:22746225
title: BOLA1 is an aerobic protein that prevents mitochondrial morphology
changes induced by glutathione depletion.
findings:
- statement: BolA family proteins localize to mitochondria
supporting_text: We show that BOLA1 is a mitochondrial protein
- statement: BOLA3 implicated in Fe-S cluster biogenesis for OXPHOS
complexes
supporting_text: BOLA3 has recently been implicated in the biogenesis of
[Fe-S] clusters for oxidative phosphorylation complexes and 2-oxo acid
dehydrogenase enzymes in mitochondria
- statement: BOLA proteins interact with GLRX5 glutaredoxin
supporting_text: A measured interaction of BOLA1 with the mitochondrial
monothiol glutaredoxin GLRX5 provides hints for potential mechanisms
behind BOLA1's effect on mitochondrial redox potential
- id: PMID:27499296
title: Mitochondrial Protein Interaction Mapping Identifies Regulators of
Respiratory Chain Function.
findings:
- statement: BOLA3-GLRX5 interaction detected in mitochondrial interactome
- id: PMID:27532772
title: Mitochondrial Bol1 and Bol3 function as assembly factors for specific
iron-sulfur proteins.
findings:
- statement: BOLA3 is a mitochondrial ISC assembly factor
supporting_text: we characterize the BOLA family proteins Bol1 and Bol3
as specific mitochondrial ISC assembly factors
- statement: BOLA3 facilitates [4Fe-4S] cluster insertion into LIAS and
SDH
supporting_text: facilitate [4Fe-4S] cluster insertion into a subset of
mitochondrial proteins such as lipoate synthase and succinate
dehydrogenase
- statement: BOLA3 forms heterocomplex with GLRX5 bridged by [2Fe-2S]
cluster
supporting_text: Bol1 and Bol3 form dimeric complexes with both
monothiol glutaredoxin Grx5 and Nfu1
- statement: Cys59 and His96 are cluster ligands in BOLA3
supporting_text: residues Cys59 and His96 are conserved within the BOLA3
proteins
- statement: BOLA3 interacts with NFU1 for [4Fe-4S] assembly
supporting_text: Bol1 and Bol3 form dimeric complexes with both
monothiol glutaredoxin Grx5 and Nfu1
- id: PMID:32296183
title: A reference map of the human binary protein interactome.
findings:
- statement: HTP protein interaction data
- id: PMID:33961781
title: Dual proteome-scale networks reveal cell-specific remodeling of the
human interactome.
findings:
- statement: HTP proteome-scale interaction data
- id: PMID:34063696
title: Molecular Basis of Multiple Mitochondrial Dysfunctions Syndrome 2
Caused by CYS59TYR BOLA3 Mutation.
findings:
- statement: C59Y mutation perturbs Fe-S cluster-binding region of BOLA3
- statement: C59Y BOLA3-GLRX5 complex still binds [2Fe-2S] cluster
- statement: Mutation forms aberrant apo BOLA3-GLRX5 complex
- statement: Explains partial phenotype recovery in some MMDS2 patients
- id: PMID:34800366
title: Quantitative high-confidence human mitochondrial proteome and its
dynamics in cellular context.
findings:
- statement: BOLA3 identified in high-confidence mitochondrial proteome
- id: file:human/BOLA3/BOLA3-deep-research-falcon.md
title: Deep research report on BOLA3
findings: []
core_functions:
- molecular_function:
id: GO:0051537
label: 2 iron, 2 sulfur cluster binding
description: BOLA3 binds a [2Fe-2S] cluster as part of the GLRX5-BOLA3
heterocomplex. The cluster is coordinated by BOLA3 Cys59 and His96
together with GLRX5 Cys67 and glutathione cysteine. Mutations in these
ligand residues cause MMDS2 (PMID:27532772, PMID:34063696).
directly_involved_in:
- id: GO:0044572
label: '[4Fe-4S] cluster assembly'
- id: GO:0016226
label: iron-sulfur cluster assembly
locations:
- id: GO:0005759
label: mitochondrial matrix
in_complex:
id: GO:1990229
label: iron-sulfur cluster assembly complex
supported_by:
- reference_id: PMID:27532772
supporting_text: we characterize the BOLA family proteins Bol1 and Bol3
as specific mitochondrial ISC assembly factors that facilitate
[4Fe-4S] cluster insertion into a subset of mitochondrial proteins
such as lipoate synthase and succinate dehydrogenase
- reference_id: PMID:34063696
supporting_text: C59Y BOLA3-GLRX5 Complex Bound a [2Fe-2S]2+ Cluster
proposed_new_terms: []
suggested_questions:
- question: What is the relative contribution of BOLA3 vs BOLA1 to different
[4Fe-4S] client proteins? Uzarska et al. showed Bol1 and Bol3 have
overlapping but distinct client specificities. Understanding this would
help interpret MMDS2 pathophysiology.
- question: Does BOLA3 have functions independent of the GLRX5-BOLA3
heterocomplex? Some interactions detected in HTP studies may represent
additional BOLA3 functions not yet characterized.
suggested_experiments:
- description: Systematic identification of all BOLA3-dependent [4Fe-4S]
client proteins using proteomics in BOLA3-deficient cells. This would
provide comprehensive understanding of BOLA3's role in [4Fe-4S] protein
maturation beyond known clients like LIAS and SDH.
hypothesis: BOLA3 deficiency affects specific subset of mitochondrial
[4Fe-4S] enzymes that can be comprehensively identified by proteomics.
- description: Structure determination of the BOLA3-GLRX5-[2Fe-2S]-NFU1
transfer complex. This would reveal mechanism of [2Fe-2S] cluster transfer
from BOLA3-GLRX5 to NFU1 for [4Fe-4S] assembly.
hypothesis: BOLA3-GLRX5 complex directly interacts with NFU1 during cluster
transfer, forming a transient ternary complex.
tags:
- iron-sulfur-cluster-biogenesis