Affinage

COX11

Cytochrome c oxidase assembly protein COX11, mitochondrial · UniProt Q9Y6N1

Length
276 aa
Mass
31.4 kDa
Annotated
2026-06-09
21 papers in source corpus 16 papers cited in narrative 16 extracted findings
Cross-family judge vs UniProt: Affinage preferred faithfulness: 7/7 claims corpus-supported (100%)

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

COX11 is a mitochondrial copper metallochaperone required for the terminal assembly of cytochrome c oxidase (CcO); it is tightly membrane-associated and dispensable for synthesis or import of CcO subunits, acting instead at a late assembly step (PMID:2167832). The protein is an intrinsic inner-membrane protein oriented with its functionally essential Cu(I)-binding C-terminal domain in the intermembrane space (IMS) and its functionless N-terminus in the matrix (PMID:15840584). This soluble C-terminal domain adopts a beta-immunoglobulin-like (beta-barrel) fold and coordinates Cu(I) through conserved cysteine thiolates, dimerizing to form a binuclear Cu(I) cluster; mutation of these cysteines abolishes copper binding and causes respiratory incompetence with reduced CcO activity (PMID:12063264, PMID:15181013). COX11 receives its copper from the Cox17 metallochaperone, which donates Cu(I) directly and specifically to Cox11 through a transfer pathway distinct from the parallel Cox17-to-Sco1 route (PMID:15199057). Copper transfer in the IMS is coupled to redox status through a dynamic, redox-regulated interaction with the twin Cx9C protein Cox19, whereby oxidation of a specific Cox11 cysteine stimulates Cox19 binding and Cox11 in turn is required for stable Cox19 accumulation (PMID:25926683). Beyond CcO assembly, COX11 contributes to cellular redox homeostasis via a conserved cysteine, acting redundantly with SOD1 under oxidative stress (PMID:34919594), and a cytosolic chaperone, RanBP2, assists Cox11 biogenesis through its leucine-rich domain while suppressing Cox11's inhibitory activity toward hexokinase I (PMID:17069463). Biallelic pathogenic COX11 variants cause infantile-onset mitochondrial encephalopathy with reduced respiration-derived ATP that is rescuable by coenzyme Q10 (PMID:36030551).

Mechanistic history

Synthesis pass · year-by-year structured walk · 16 steps
  1. 1990 High

    Established that COX11 is needed for cytochrome c oxidase function without being a structural subunit, defining it as a dedicated assembly factor acting at a terminal stage.

    Evidence Yeast cox11 mutant genetics, biochemical fractionation, and immunoblotting of CcO subunits

    PMID:2167832

    Open questions at the time
    • Did not identify the molecular activity of COX11
    • Membrane topology unresolved
    • No mechanistic link to copper or any cofactor
  2. 1993 Medium

    An early attempt to assign biochemical function proposed COX11 in heme A biosynthesis based on heme O accumulation in mutants, later superseded by the copper chaperone role.

    Evidence Heme chromatographic analysis of cox11 yeast mutants

    PMID:8118433

    Open questions at the time
    • Correlative heme phenotype, no direct enzymatic activity demonstrated
    • Interpretation not borne out by subsequent copper studies
  3. 1998 Medium

    Showed the human ortholog is mitochondrially targeted and conserves functional domains, extending the yeast paradigm to humans.

    Evidence In vitro mitochondrial import and protease-protection assays, sequence alignment

    PMID:9878253

    Open questions at the time
    • Did not test functional complementation in human cells
    • No molecular activity assigned to human protein
  4. 2002 High

    Identified COX11 as a Cu(I)-binding protein whose conserved cysteines coordinate copper and are essential for respiration, defining its molecular activity as copper handling.

    Evidence In vitro Cu(I) binding, EXAFS, cysteine mutagenesis with respiratory and CcO activity readouts

    PMID:12063264

    Open questions at the time
    • Copper donor and acceptor not yet identified
    • Did not establish structural fold or topology
  5. 2004 High

    Resolved the copper-binding domain fold and showed Cu(I)-dependent dimerization producing a bridged binuclear cluster, providing the structural basis for metal coordination.

    Evidence NMR solution structure of bacterial Cox11 soluble domain with EXAFS and dimerization assays

    PMID:15181013

    Open questions at the time
    • Structure from bacterial ortholog, not human
    • No structure of full-length membrane-embedded protein
  6. 2004 High

    Identified Cox17 as the specific upstream copper donor to Cox11 via a pathway distinct from the Cox17-Sco1 route, placing Cox11 in a defined copper relay.

    Evidence In vitro copper transfer with purified proteins, Cox17 C57Y mutant, yeast cytoplasmic co-expression

    PMID:15199057

    Open questions at the time
    • Did not directly demonstrate copper donation from Cox11 to the Cu(B) site of Cox1
    • Kinetics of transfer not quantified
  7. 2005 High

    Mapped COX11 topology, placing the essential copper domain in the IMS and showing the matrix N-terminus is dispensable, and revealed species-specific requirements of the copper domain.

    Evidence Protease protection in mitoplasts, complementation with fusion and chimeric constructs

    PMID:15840584

    Open questions at the time
    • Reason the human copper domain cannot replace yeast not resolved
    • Mechanism of membrane insertion unaddressed
  8. 2005 Low

    Reported a COX11 interaction with ACDP4 linked to metal-ion toxicity, hinting at broader metal homeostasis coupling.

    Evidence Yeast two-hybrid, HEK293 co-expression, metal toxicity assays

    PMID:15840172

    Open questions at the time
    • No reciprocal Co-IP or direct biochemical confirmation of the interaction
    • Functional significance for CcO assembly untested
  9. 2006 Medium

    Uncovered a cytosolic chaperone (RanBP2) for Cox11 biogenesis and a moonlighting Cox11 activity inhibiting hexokinase I that RanBP2 suppresses.

    Evidence Reciprocal in vitro/in vivo binding, chaperone and HKI activity assays, colocalization, RanBP2 haploinsufficient mouse

    PMID:17069463

    Open questions at the time
    • Physiological relevance of HKI inhibition in vivo unclear
    • Connection between cytosolic chaperoning and mitochondrial import not resolved
  10. 2015 High

    Demonstrated redox-regulated coupling between Cox11 and Cox19, linking IMS redox state to copper transfer during CcO biogenesis.

    Evidence SILAC proteomics, Co-IP, mutagenesis of Cox19 Tyr-Leu dipeptides and Cox11 cysteines, stability assays

    PMID:25926683

    Open questions at the time
    • Direct effect of Cox19 binding on copper transfer rate not measured
    • Identity of the modifying oxidant unknown
  11. 2021 Medium

    Established a CcO-independent antioxidant role for COX11 acting redundantly with SOD1, broadening its function beyond copper delivery.

    Evidence ROS measurement and genetic epistasis in yeast and Arabidopsis, cysteine mutagenesis, oxidative stress growth assays

    PMID:34919594

    Open questions at the time
    • Biochemical mechanism of antioxidant activity not defined
    • Relevance to human disease unestablished
  12. 2021 Low

    Linked a disease RANBP2 mutation to impaired RANBP2-COX11 binding, connecting the chaperone interaction to encephalopathy.

    Evidence GST pull-down with wild-type and mutant RANBP2

    PMID:34400285

    Open questions at the time
    • Single pull-down without downstream functional readout
    • No demonstration that reduced binding alters COX11 function in patients
  13. 2021 Low

    Described post-transcriptional regulation of COX11 by miR-10a-3p coupled to NF-kB activation in macrophages.

    Evidence Dual luciferase reporter, miRNA mimic/inhibitor transfection, NF-kB Western blots in THP-1 cells

    PMID:34659807

    Open questions at the time
    • Causal link between COX11 downregulation and NF-kB activation not mechanistically resolved
    • Single cell model
  14. 2022 Medium

    Established COX11 as a human disease gene, with biallelic variants causing infantile mitochondrial encephalopathy and CoQ10-rescuable ATP deficiency.

    Evidence Trio exome/genome sequencing, patient fibroblast ATP assays, CoQ10 rescue across two families

    PMID:36030551

    Open questions at the time
    • Mechanism connecting COX11 to CoQ10-dependent metabolism not established
    • Limited number of families
  15. 2023 Medium

    Extended the disease spectrum with heterozygous variants modeled in yeast, correlating reduced respiration and redox defects with patient oxidative stress sensitivity.

    Evidence Humanized yeast complementation, respiration and ROS assays, patient fibroblast stress assays, in silico structure analysis

    PMID:38068960

    Open questions at the time
    • Structural impact inferred in silico, not experimentally
    • Single lab
  16. 2025 Medium

    Showed PTBP3-driven exon 4 skipping produces a hypofunctional COX11 isoform that lowers mitochondrial copper and lets tumor cells evade cuproptosis, identifying a therapeutic vulnerability.

    Evidence Full-length transcriptome sequencing, PTBP3 manipulation in gastric cancer cells and organoids, ASO plus copper ionophore treatment in xenografts

    PMID:40270362

    Open questions at the time
    • Link between exon 4 and copper transport inferred rather than biochemically reconstituted
    • Single lab

Open questions

Synthesis pass · forward-looking unresolved questions
  • How copper is handed from Cox11 to the Cu(B) site of Cox1, and the mechanistic basis of the CoQ10-rescuable energy defect in patients, remain unresolved.
  • No direct demonstration of Cu transfer from Cox11 to Cox1 in the timeline
  • Mechanism of CoQ10 rescue undefined
  • No high-resolution structure of human full-length COX11

Mechanism profile

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0140104 molecular carrier activity 3 GO:0016209 antioxidant activity 1
Localization
GO:0005739 mitochondrion 3
Pathway
R-HSA-1852241 Organelle biogenesis and maintenance 2 R-HSA-1430728 Metabolism 1
Partners
COX17COX19RANBP2

Evidence

Reading pass · 16 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
1990 COX11 encodes a 28 kDa protein tightly associated with the mitochondrial membrane that is required for cytochrome c oxidase assembly but is not a component of purified cytochrome oxidase; loss of COX11 does not affect synthesis or mitochondrial import of cytochrome oxidase subunit polypeptides, suggesting COX11 acts at a terminal assembly stage. Yeast genetics (cox11 mutant characterization), immunoblotting with anti-Cox11 antibody, analysis of cytochrome oxidase subunits in wild-type vs. cox11 mutant The EMBO journal High 2167832
1993 Analysis of heme constituents in a cox11 mutant revealed absence of heme A and presence of a heme with chromatographic properties of heme O, suggesting COX11 protein may participate in a step of heme A biosynthesis (conversion of heme O to heme A by forming the formyl group), distinct from COX10's farnesyl transferase activity. Heme chromatographic analysis of cox11 yeast mutants Biochemistry and molecular biology international Medium 8118433
1998 Human COX11 protein is targeted to mitochondria, as demonstrated by in vitro import and protease-protection assays, and shows significant amino acid identity to yeast Cox11 with conservation of functional domains. In vitro mitochondrial import assay, protease-protection assay, sequence alignment Genomics Medium 9878253
2002 Cox11 is a Cu(I)-binding protein; its soluble C-terminal domain forms a dimer coordinating one Cu(I) per monomer via three thiolate ligands (conserved Cys residues), forming a binuclear Cu(I) cluster. Mutation of any conserved Cys reduces Cu(I) binding and confers respiratory incompetence with reduced cytochrome c oxidase activity. In vitro Cu(I) binding assays, X-ray absorption spectroscopy (EXAFS), site-directed mutagenesis of Cys residues, respiratory growth assay, cytochrome c oxidase activity measurement The Journal of biological chemistry High 12063264
2004 Cox17 is a specific copper donor to both Sco1 and Cox11 in vitro; purified CuCox17 directly transfers Cu to Cox11 (and Sco1) but not to heterologous proteins (BSA, carbonic anhydrase). A C57Y mutant of Cox17 fails to transfer copper to Sco1 but remains competent for copper transfer to Cox11, demonstrating distinct transfer pathways. Metallation of soluble Cox11 expressed in the yeast cytoplasm requires co-expression of Cox17. In vitro copper transfer assay with purified proteins, site-directed mutagenesis of Cox17 (C57Y), yeast cytoplasm expression system with co-expression of soluble Cox11/Sco1 domains The Journal of biological chemistry High 15199057
2004 The solution structure of the Cox11 soluble domain (from Sinorhizobium meliloti) reveals a novel beta-immunoglobulin-like fold (beta-barrel); the copper-binding motif with two conserved cysteines is on one face of the barrel. The apoprotein is monomeric with DTT but dimerizes without reductant; Cu(I) binding (confirmed by NMR and EXAFS) induces a dimeric state with two thiolates bridging two Cu(I) ions. NMR solution structure determination, EXAFS, biochemical dimerization assays The Journal of biological chemistry High 15181013
2005 Cox11 is oriented with its Cu(I)-binding C-terminal domain (~189 residues) exposed in the mitochondrial intermembrane space (IMS) and its N-terminus projecting into the matrix, as shown by protease susceptibility of a C-terminal Myc tag in mitoplasts. The matrix domain of Cox11 lacks a specific function, whereas the Cu(I)-binding/donating function requires the yeast Cox11 IMS sequence; the human Cox11 copper domain cannot functionally replace the yeast sequence. Protease protection assay in mitoplasts (topology mapping), functional complementation with Cox11-Rsm22 fusion proteins, SCO1/COX11 chimera analysis The Journal of biological chemistry High 15840584
2005 ACDP4 specifically interacts with COX11 (identified by yeast two-hybrid and confirmed in vitro and in vivo); co-expression of ACDP4 and COX11 in HEK293 cells enhances toxicity to copper, manganese, and cobalt compared to either alone, indicating functional coupling in metal ion homeostasis. Yeast two-hybrid screen, co-expression in HEK293 cells, metal ion toxicity assay Molecular pain Low 15840172
2006 RanBP2 associates with Cox11 in vitro and in vivo via its leucine-rich domain and colocalizes with Cox11; RanBP2's leucine-rich domain exhibits chaperone activity toward intermediate and mature folding species of Cox11, supporting a cytosolic chaperone role during Cox11 biogenesis. Cox11 is a strong inhibitor of hexokinase I (HKI), and RanBP2 suppresses this inhibitory activity of Cox11 over HKI. Co-immunoprecipitation (in vivo), in vitro binding assays, chaperone activity assay, HKI activity assay, co-localization studies, RanBP2 haploinsufficient mouse model PLoS genetics Medium 17069463
2015 Cox19 (a twin Cx9C IMS protein) interacts dynamically with Cox11 in a redox-regulated manner; Cox11 interaction is critical for stable accumulation of Cox19 in mitochondria. An oxidative modification of a specific cysteine in Cox11 stimulates Cox19 binding via hydrophobic surface residues (conserved Tyr-Leu dipeptides in Cox19), coupling redox status to copper transfer in the IMS during cytochrome c oxidase biogenesis. SILAC-based quantitative proteomics, co-immunoprecipitation, mutagenesis of Cox19 Tyr-Leu dipeptides and Cox11 Cys residues, mitochondrial protein stability assays Molecular biology of the cell High 25926683
2021 RANBP2 missense mutation (c.1754C>T) causing autosomal dominant acute necrotizing encephalopathy significantly attenuates binding of mutant RANBP2 to COX11 in a GST pull-down assay, linking impaired RANBP2-COX11 interaction to disease pathophysiology. GST pull-down assay with recombinant wild-type and mutant RANBP2 proteins Neuroscience letters Low 34400285
2021 COX11 has an additional role in cellular redox homeostasis independent of COX assembly: overexpression of Cox11 reduces ROS levels under oxidative stress (paraquat), while COX11 knockout/knockdown reduces ROS levels under normal conditions. Cox11 is functionally redundant with superoxide dismutase 1 (SOD1) under paraquat stress. The conserved Cys219 (AtCOX11) and Cys208 (ScCOX11) are important for this antioxidative function. Overexpression of soluble COX11 variants improves resistance to menadione. ROS measurement (yeast and Arabidopsis), genetic epistasis (ΔSccox11ΔScsod1 double mutant), growth assays under oxidative stress, overexpression of soluble Cox11 variants with cysteine mutations PloS one Medium 34919594
2022 Biallelic pathogenic variants in human COX11 cause infantile-onset mitochondrial encephalopathy with decreased cellular ATP levels derived from respiration; ATP levels can be rescued by coenzyme Q10 supplementation, revealing an unexpected functional connection between COX11 and CoQ10-dependent energy metabolism. Trio genome/exome sequencing, functional studies in patient fibroblasts (ATP measurement), CoQ10 rescue experiment Human mutation Medium 36030551
2021 miR-10a-3p directly targets COX11 mRNA (confirmed by dual luciferase reporter assay); increased miR-10a-3p downregulates COX11 expression and activates the NF-κB signaling pathway (decreased IκBα, increased p-IKKα/β and p-p65) in THP-1 macrophages stimulated with Mycoplasma pneumoniae lipid-associated membrane proteins. Dual luciferase reporter assay, miR-10a-3p mimic/inhibitor transfection in THP-1 cells, Western blot for NF-κB pathway components Journal of thoracic disease Low 34659807
2023 Novel heterozygous COX11 variants in a patient with Leigh-like features show differential effects on yeast growth, respiration, and cellular redox status when modeled in S. cerevisiae; patient fibroblasts show increased sensitivity to oxidative stress. In silico structural analysis suggests impact on human COX11 protein stability and function. Yeast complementation assay with humanized COX11 mutations, respiration measurement, ROS assays, patient fibroblast oxidative stress sensitivity, in silico structure-based analysis International journal of molecular sciences Medium 38068960
2025 PTBP3-mediated exon 4 skipping in COX11 pre-mRNA generates shorter COX11 transcripts with impaired protein function, reducing mitochondrial copper content and enabling tumor cells to evade cuproptosis. Full-length COX11 is required for proper mitochondrial copper accumulation; antisense oligonucleotides (ASOs) targeting the short COX11 transcripts combined with copper ionophores trigger cuproptosis in gastric cancer models. Full-length transcriptome sequencing, gastric cancer cells and patient-derived organoids with PTBP3 manipulation, PDO-based xenograft models, ASO treatment combined with copper ionophores Advanced science Medium 40270362

Source papers

Stage 0 corpus · 21 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
2004 Specific copper transfer from the Cox17 metallochaperone to both Sco1 and Cox11 in the assembly of yeast cytochrome C oxidase. The Journal of biological chemistry 244 15199057
1990 Cytochrome oxidase assembly in yeast requires the product of COX11, a homolog of the P. denitrificans protein encoded by ORF3. The EMBO journal 154 2167832
2002 Yeast Cox11, a protein essential for cytochrome c oxidase assembly, is a Cu(I)-binding protein. The Journal of biological chemistry 136 12063264
1998 Identification and characterization of human cDNAs specific to BCS1, PET112, SCO1, COX15, and COX11, five genes involved in the formation and function of the mitochondrial respiratory chain. Genomics 122 9878253
1993 On the functions of the yeast COX10 and COX11 gene products. Biochemistry and molecular biology international 94 8118433
2006 RanBP2 modulates Cox11 and hexokinase I activities and haploinsufficiency of RanBP2 causes deficits in glucose metabolism. PLoS genetics 93 17069463
2016 Transcriptome analysis of copper homeostasis genes reveals coordinated upregulation of SLC31A1,SCO1, and COX11 in colorectal cancer. FEBS open bio 91 27516958
2004 Solution structure of Cox11, a novel type of beta-immunoglobulin-like fold involved in CuB site formation of cytochrome c oxidase. The Journal of biological chemistry 75 15181013
2015 Redox-regulated dynamic interplay between Cox19 and the copper-binding protein Cox11 in the intermembrane space of mitochondria facilitates biogenesis of cytochrome c oxidase. Molecular biology of the cell 59 25926683
2005 Functional analysis of the domains in Cox11. The Journal of biological chemistry 45 15840584
2005 Physical interaction and functional coupling between ACDP4 and the intracellular ion chaperone COX11, an implication of the role of ACDP4 in essential metal ion transport and homeostasis. Molecular pain 23 15840172
1999 Mutant allele pso7-1, that sensitizes Saccharomyces cerevisiae to photoactivated psoralen, is allelic with COX11, encoding a protein indispensable for a functional cytochrome c oxidase. Current genetics 16 10501934
2025 Targeting PTBP3-Mediated Alternative Splicing of COX11 Induces Cuproptosis for Inhibiting Gastric Cancer Peritoneal Metastasis. Advanced science (Weinheim, Baden-Wurttemberg, Germany) 13 40270362
2023 Mitochondrial-targeting effector RsIA_CtaG/Cox11 in Rhizoctonia solani AG-1 IA has two functions: plant immunity suppression and cell death induction mediated by a rice cytochrome c oxidase subunit. Molecular plant pathology 10 37902589
2022 Biallelic pathogenic variants in COX11 are associated with an infantile-onset mitochondrial encephalopathy. Human mutation 10 36030551
2021 RANBP2 mutation causing autosomal dominant acute necrotizing encephalopathy attenuates its interaction with COX11. Neuroscience letters 10 34400285
2021 The mitochondrial copper chaperone COX11 has an additional role in cellular redox homeostasis. PloS one 10 34919594
2021 The role of targeted regulation of COX11 by miR-10a-3p in the development and progression of paediatric mycoplasma pneumoniae pneumonia. Journal of thoracic disease 7 34659807
2023 Novel COX11 Mutations Associated with Mitochondrial Disorder: Functional Characterization in Patient Fibroblasts and Saccharomyces cerevisiae. International journal of molecular sciences 6 38068960
2023 LncRNA FGD5-AS1 Alleviates Inflammation in Allergic Rhinitis through the miR-223-3p/COX11 Axis. International archives of allergy and immunology 4 38071964
2022 Expression and copper binding characteristics of Plasmodium falciparum cytochrome c oxidase assembly factor 11, Cox11. Malaria journal 3 35672733

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