id: Q8NI60
gene_symbol: COQ8A
product_type: PROTEIN
status: INITIALIZED
taxon:
  id: NCBITaxon:9606
  label: Homo sapiens
description: >-
  COQ8A (also known as ADCK3, CABC1, COQ8) is a mitochondrial member of the ancient UbiB
  family of atypical protein-kinase-like (PKL) enzymes, and is one of two human co-orthologs
  (with COQ8B/ADCK4) of yeast Coq8p. It is required for the biosynthesis of coenzyme Q
  (ubiquinone/CoQ10), a lipid-soluble electron carrier of the respiratory chain and a
  membrane antioxidant. The 647-residue precursor is imported into mitochondria (an
  N-terminal transit peptide of ~162 residues is removed) and anchors to the inner
  mitochondrial membrane as a single-pass membrane protein, with its catalytic domain facing
  the matrix, where CoQ is produced. Although COQ8A adopts a protein-kinase-like fold, several
  UbiB-specific features suppress canonical protein-kinase activity: an N-terminal KxGQ domain
  occludes the substrate-binding cleft, and an alanine-rich (AAAS) loop replaces the canonical
  glycine-rich nucleotide-binding loop, conferring an unusual selectivity for binding ADP over
  ATP. Biochemically, the protein binds and hydrolyzes ATP (ATPase activity that is enhanced by
  the KxGQ motif and by coenzyme-Q head-group intermediates and cardiolipin), and it interacts
  with lipid CoQ intermediates, rather than exhibiting canonical protein-kinase phosphotransfer
  in trans. Functionally, COQ8A stabilizes and helps assemble the multi-subunit CoQ biosynthetic
  complex (the "COQ synthome"/complex Q; COQ3-COQ7, COQ9), thereby streamlining CoQ production.
  Biallelic loss-of-function variants cause primary coenzyme Q10 deficiency-4 (COQ10D4),
  presenting as autosomal-recessive cerebellar ataxia (ARCA2/SCAR9) with cerebellar atrophy,
  exercise intolerance, and variable seizures.
alternative_products:
- name: '1'
  id: Q8NI60-1
- name: '2'
  id: Q8NI60-2
  sequence_note: VSP_022351
- name: '3'
  id: Q8NI60-3
  sequence_note: VSP_022353
- name: '4'
  id: Q8NI60-4
  sequence_note: VSP_022352
existing_annotations:
- term:
    id: GO:0006744
    label: ubiquinone biosynthetic process
  evidence_type: IBA
  original_reference_id: GO_REF:0000033
  qualifier: involved_in
  review:
    summary: >-
      Phylogenetic (PAN-GO) inference of the core, well-established role of COQ8A/Coq8p
      orthologs in ubiquinone (coenzyme Q) biosynthesis. This is consistent with abundant
      experimental evidence and is the central function of the gene.
    action: ACCEPT
    supported_by:
    - reference_id: file:human/COQ8A/COQ8A-uniprot.txt
      supporting_text: Atypical kinase involved in the biosynthesis of coenzyme Q
- term:
    id: GO:0031966
    label: mitochondrial membrane
  evidence_type: IEA
  original_reference_id: GO_REF:0000044
  qualifier: located_in
  review:
    summary: >-
      Electronic mapping from the UniProt Subcellular Location keyword (mitochondrion membrane).
      Correct and corroborated by experimental localization; mitochondrial (inner) membrane
      association is well established. Kept as non-core relative to the more specific matrix/inner
      membrane localization.
    action: KEEP_AS_NON_CORE
    supported_by:
    - reference_id: file:human/COQ8A/COQ8A-uniprot.txt
      supporting_text: Mitochondrion membrane
- term:
    id: GO:0005515
    label: protein binding
  evidence_type: IPI
  original_reference_id: PMID:16189514
  qualifier: enables
  review:
    summary: >-
      Bare "protein binding" (GO:0005515) from a large-scale human protein-protein interaction
      network study (IntAct partner Q9UI14/RABAC1). The generic term conveys no specific molecular
      function and the partner is not part of the CoQ biosynthetic machinery. Over-annotation of a
      high-throughput binary interaction; not a core function.
    action: MARK_AS_OVER_ANNOTATED
- term:
    id: GO:0005515
    label: protein binding
  evidence_type: IPI
  original_reference_id: PMID:25416956
  qualifier: enables
  review:
    summary: >-
      Bare "protein binding" from a proteome-scale human interactome map (Rolland et al.).
      Multiple binary partners captured (e.g. AGTRAP, TMEM239, LDAF1, REEP6, TFIP11, RABAC1);
      none are CoQ-biosynthesis proteins and the term is uninformative. High-throughput
      over-annotation; not a core function.
    action: MARK_AS_OVER_ANNOTATED
- term:
    id: GO:0005515
    label: protein binding
  evidence_type: IPI
  original_reference_id: PMID:25910212
  qualifier: enables
  review:
    summary: >-
      Bare "protein binding" from a study of macromolecular interaction perturbations in genetic
      disorders (Sahni et al.). Binary partners (DTX2, SH3GLB1, REEP6, TFIP11, etc.) are not CoQ
      pathway components; the generic term is uninformative. High-throughput over-annotation.
    action: MARK_AS_OVER_ANNOTATED
- term:
    id: GO:0005515
    label: protein binding
  evidence_type: IPI
  original_reference_id: PMID:27499296
  qualifier: enables
  review:
    summary: >-
      Bare "protein binding" from mitochondrial protein interaction mapping (Floyd et al.); the
      IntAct partner here is COQ9 (O75208), a genuine member of the CoQ biosynthetic complex
      ("complex Q"). The interaction is biologically real and central to COQ8A function, but the
      generic GO:0005515 term does not capture it. Marked as over-annotated at the term level;
      the underlying complex membership is represented via in_complex in core_functions.
    action: MARK_AS_OVER_ANNOTATED
    supported_by:
    - reference_id: file:human/COQ8A/COQ8A-uniprot.txt
      supporting_text: composed of at least COQ3, COQ4, COQ5, COQ6, COQ7 and COQ9
- term:
    id: GO:0005515
    label: protein binding
  evidence_type: IPI
  original_reference_id: PMID:31515488
  qualifier: enables
  review:
    summary: >-
      Bare "protein binding" from a systematic study of interaction disruption by genetic variants
      (Fragoza et al.). Partners (AGTRAP, REEP6, TFIP11) are not CoQ-pathway proteins; term is
      uninformative. High-throughput over-annotation; not a core function.
    action: MARK_AS_OVER_ANNOTATED
- term:
    id: GO:0005515
    label: protein binding
  evidence_type: IPI
  original_reference_id: PMID:32296183
  qualifier: enables
  review:
    summary: >-
      Bare "protein binding" from the HuRI human binary interactome reference map (Luck et al.).
      Many low-specificity Y2H partners captured; none are CoQ-biosynthesis components and the
      generic term is uninformative. High-throughput over-annotation; not a core function.
    action: MARK_AS_OVER_ANNOTATED
- term:
    id: GO:0005515
    label: protein binding
  evidence_type: IPI
  original_reference_id: PMID:32814053
  qualifier: enables
  review:
    summary: >-
      Bare "protein binding" from an interactome map of neurodegenerative-disease proteins.
      Partners (MAOB, LITAF, SPRY4, ATG10, etc.) are not CoQ-pathway components; the generic
      term is uninformative. High-throughput over-annotation; not a core function.
    action: MARK_AS_OVER_ANNOTATED
- term:
    id: GO:0006744
    label: ubiquinone biosynthetic process
  evidence_type: IEA
  original_reference_id: GO_REF:0000041
  qualifier: involved_in
  review:
    summary: >-
      Electronic annotation from UniPathway vocabulary mapping (ubiquinone biosynthesis,
      UPA00232). Correct and consistent with the core function, though redundant with the
      experimental IMP/IDA annotations to the same term.
    action: ACCEPT
    supported_by:
    - reference_id: file:human/COQ8A/COQ8A-uniprot.txt
      supporting_text: Cofactor biosynthesis; ubiquinone biosynthesis.
- term:
    id: GO:0005739
    label: mitochondrion
  evidence_type: IDA
  original_reference_id: GO_REF:0000052
  qualifier: located_in
  review:
    summary: >-
      Mitochondrial localization from HPA immunofluorescence curation. Correct; COQ8A is a
      well-established mitochondrial protein. Kept as non-core relative to the more specific
      inner-membrane/matrix-facing localization.
    action: KEEP_AS_NON_CORE
- term:
    id: GO:0031966
    label: mitochondrial membrane
  evidence_type: EXP
  original_reference_id: PMID:11888884
  qualifier: located_in
  review:
    summary: >-
      Experimental mitochondrial membrane localization from the original CABC1/COQ8A isolation
      study (Iiizumi et al.), which identified CABC1 as a mitochondrial, p53-inducible protein.
      Consistent with the well-established inner-mitochondrial-membrane localization. Accepted as
      the core localization; the mature protein is a single-pass inner-membrane protein with a
      matrix-facing catalytic domain.
    action: ACCEPT
    supported_by:
    - reference_id: file:human/COQ8A/COQ8A-uniprot.txt
      supporting_text: Single-pass membrane protein
- term:
    id: GO:0031966
    label: mitochondrial membrane
  evidence_type: EXP
  original_reference_id: PMID:25498144
  qualifier: located_in
  review:
    summary: >-
      Experimental mitochondrial-membrane localization from the structural/biochemical study
      (Stefely et al. 2015), which mapped the mature form and confirmed matrix-facing residence
      at the inner membrane. Accepted; corroborates the core localization.
    action: ACCEPT
    supported_by:
    - reference_id: PMID:25498144
      supporting_text: ADCK3 is known to reside in the mitochondrial matrix
- term:
    id: GO:0031966
    label: mitochondrial membrane
  evidence_type: EXP
  original_reference_id: PMID:33988507
  qualifier: located_in
  review:
    summary: >-
      Mitochondrial-membrane localization from the subcellular kinome map (Zhang et al. 2021),
      a systematic assignment of kinome members to compartments. Consistent with the established
      mitochondrial localization; corroborating, non-core.
    action: KEEP_AS_NON_CORE
- term:
    id: GO:0004672
    label: protein kinase activity
  evidence_type: ISS
  original_reference_id: GO_REF:0000024
  qualifier: enables
  review:
    summary: >-
      "Protein kinase activity" transferred by sequence similarity from COQ8B (Q96D53). Although
      COQ8A adopts a protein-kinase-like fold, direct biochemical study demonstrated that it
      lacks canonical protein kinase activity in trans (the same PMID:27499294 result underpins
      an explicit NOT protein-kinase-activity annotation on this gene). The demonstrated activity
      is instead ATP binding/hydrolysis (ATPase). This ISS annotation therefore over-asserts a
      canonical protein-kinase function; recommend replacing with ATP binding and ATP hydrolysis
      (ATPase) activity, which the evidence supports.
    action: MODIFY
    proposed_replacement_terms:
    - id: GO:0005524
      label: ATP binding
    - id: GO:0016887
      label: ATP hydrolysis activity
    supported_by:
    - reference_id: PMID:27499294
      supporting_text: interacts with lipid CoQ intermediates
- term:
    id: GO:0006744
    label: ubiquinone biosynthetic process
  evidence_type: IDA
  original_reference_id: PMID:38425362
  qualifier: involved_in
  review:
    summary: >-
      Direct evidence that COQ8 promotes coenzyme Q biosynthesis, from in-vitro reconstruction of
      the animal COQ metabolon (Nicoll et al. 2024), which shows COQ8 increases and streamlines CoQ
      production. (The experimentally characterized paralog in that study was ancestral COQ8B, since
      recombinant COQ8A gave very low yields, but COQ8A and COQ8B are chordate co-orthologs of the
      same COQ8 clade and the CoQ-biosynthesis role is shared.) Accepts the gene's core biological
      process.
    action: ACCEPT
    supported_by:
    - reference_id: PMID:38425362
      supporting_text: increases and streamlines coenzyme Q production
- term:
    id: GO:0005739
    label: mitochondrion
  evidence_type: HTP
  original_reference_id: PMID:34800366
  qualifier: located_in
  review:
    summary: >-
      Mitochondrion localization from a high-throughput high-confidence mitochondrial proteome
      study. Consistent with the established localization; corroborating, non-core.
    action: KEEP_AS_NON_CORE
- term:
    id: GO:0005739
    label: mitochondrion
  evidence_type: IDA
  original_reference_id: PMID:33988507
  qualifier: located_in
  review:
    summary: >-
      Mitochondrion localization (IDA) from the subcellular kinome map (Zhang et al. 2021).
      Correct and consistent with the well-established mitochondrial localization; corroborating.
    action: KEEP_AS_NON_CORE
- term:
    id: GO:0004672
    label: protein kinase activity
  evidence_type: IDA
  original_reference_id: PMID:27499294
  qualifier: enables
  negated: true
  review:
    summary: >-
      NOT protein kinase activity. Stefely et al. 2016 directly demonstrated that COQ8, despite
      its protein-kinase-like fold, lacks canonical protein kinase activity in trans. This negated
      annotation is correct and important — it explicitly counters the naive "protein kinase"
      assignment implied by the family name (ADCK, aarF domain-containing kinase). Accept as-is.
    action: ACCEPT
    supported_by:
    - reference_id: PMID:27499294
      supporting_text: 'Instead, COQ8 has ATPase activity'
- term:
    id: GO:0006468
    label: protein phosphorylation
  evidence_type: IDA
  original_reference_id: PMID:27499294
  qualifier: involved_in
  negated: true
  review:
    summary: >-
      NOT involved_in protein phosphorylation. Consistent with the finding that COQ8 does not
      perform canonical protein-kinase phosphotransfer in trans; the protein instead functions via
      ATPase / small-molecule (possibly lipid) activity and complex-Q stabilization. Correct
      negated annotation; accept as-is.
    action: ACCEPT
    supported_by:
    - reference_id: PMID:27499294
      supporting_text: interacts with lipid CoQ intermediates
- term:
    id: GO:0006744
    label: ubiquinone biosynthetic process
  evidence_type: IMP
  original_reference_id: PMID:27499294
  qualifier: involved_in
  review:
    summary: >-
      IMP evidence that COQ8A is required for ubiquinone biosynthesis: Coq8a-knockout mice develop
      cerebellar ataxia recapitulating ARCA2 with disruption of complex Q and CoQ deficiency, and
      active-site mutations abolish CoQ production. This is the core biological process of the gene.
      Accept.
    action: ACCEPT
    supported_by:
    - reference_id: PMID:27499294
      supporting_text: the K134H mutation eliminates CoQ production in vivo
- term:
    id: GO:0016301
    label: kinase activity
  evidence_type: IDA
  original_reference_id: PMID:27499294
  qualifier: enables
  review:
    summary: >-
      Generic "kinase activity" IDA. The activity actually measured in this paper is ATP hydrolysis
      (ATPase), which the authors describe as small-molecule "water kinase" activity and which is
      enhanced by the UbiB-specific KxGQ motif. The broad "kinase activity" term is imprecise and,
      given the explicit NOT protein kinase annotation, risks implying phosphotransfer to a
      macromolecular substrate that was not demonstrated. Recommend the more precise ATP hydrolysis
      (ATPase) activity term.
    action: MODIFY
    proposed_replacement_terms:
    - id: GO:0016887
      label: ATP hydrolysis activity
    supported_by:
    - reference_id: PMID:27499294
      supporting_text: Coq8p ATPase activity is enhanced by the UbiB-specific KxGQ motif
- term:
    id: GO:0016310
    label: phosphorylation
  evidence_type: IDA
  original_reference_id: PMID:27499294
  qualifier: involved_in
  review:
    summary: >-
      Generic BP "phosphorylation" paired with the "kinase activity" MF. The only phosphotransfer
      demonstrated for COQ8 is autophosphorylation, and that is seen only when the native A-rich
      loop is mutated (A-to-G); native COQ8 does not carry out canonical protein phosphorylation
      (NOT-annotated). The measured wild-type activity is ATP hydrolysis. "Phosphorylation" as a
      biological process is an over-annotation here and is not the gene's endogenous role
      (ubiquinone biosynthesis).
    action: MARK_AS_OVER_ANNOTATED
- term:
    id: GO:0005739
    label: mitochondrion
  evidence_type: IDA
  original_reference_id: PMID:25498144
  qualifier: located_in
  review:
    summary: >-
      Mitochondrion localization (IDA) from Stefely et al. 2015, which characterized endogenous
      ADCK3/COQ8A as residing in the mitochondrial matrix at the inner membrane. Correct;
      corroborating the core localization.
    action: KEEP_AS_NON_CORE
    supported_by:
    - reference_id: PMID:25498144
      supporting_text: ADCK3 is known to reside in the mitochondrial matrix
- term:
    id: GO:0006744
    label: ubiquinone biosynthetic process
  evidence_type: IMP
  original_reference_id: PMID:25498144
  qualifier: involved_in
  review:
    summary: >-
      IMP evidence for the ubiquinone-biosynthesis role: structure-guided mutations of conserved
      nucleotide-pocket, A-rich loop and QKE-triad residues in Coq8p/ADCK3 eliminate respiratory
      growth and reduce CoQ abundance in vivo. Core biological process; accept.
    action: ACCEPT
    supported_by:
    - reference_id: PMID:25498144
      supporting_text: A single alanine-to-glycine mutation of this loop flips
- term:
    id: GO:0016301
    label: kinase activity
  evidence_type: IDA
  original_reference_id: PMID:25498144
  qualifier: enables
  review:
    summary: >-
      Generic "kinase activity" IDA. The demonstrable ATP-utilizing activity in this study is
      autophosphorylation enabled only by the engineered A339G mutation of the A-rich loop; wild-type
      ADCK3 shows an unusual ADP-over-ATP selectivity and does not display canonical kinase activity.
      The umbrella "kinase activity" term over-asserts the native biochemistry; the better-supported
      activities are ATP binding and (per PMID:27499294) ATP hydrolysis.
    action: MODIFY
    proposed_replacement_terms:
    - id: GO:0016887
      label: ATP hydrolysis activity
    supported_by:
    - reference_id: PMID:25498144
      supporting_text: unusual selectivity for binding ADP over ATP
- term:
    id: GO:0016310
    label: phosphorylation
  evidence_type: IDA
  original_reference_id: PMID:25498144
  qualifier: involved_in
  review:
    summary: >-
      Generic BP "phosphorylation", paired with the "kinase activity" MF above. Based on
      autophosphorylation that is only unmasked by the artificial A339G mutation and that inhibits
      CoQ biosynthesis in vivo — i.e. not the gene's native process. Over-annotation; the endogenous
      process is ubiquinone biosynthesis.
    action: MARK_AS_OVER_ANNOTATED
- term:
    id: GO:0043531
    label: ADP binding
  evidence_type: IDA
  original_reference_id: PMID:25498144
  qualifier: enables
  review:
    summary: >-
      ADP binding (IDA). A distinctive and well-supported molecular feature of COQ8A: thermal-shift
      assays show adenine nucleotides stabilize the protein, with an unusual selectivity for ADP
      over ATP driven by the A-rich (AAAS) loop. This nucleotide-binding activity is central to the
      atypical UbiB mechanism. Accept.
    action: ACCEPT
    supported_by:
    - reference_id: PMID:25498144
      supporting_text: unusual selectivity for binding ADP over ATP
- term:
    id: GO:0005759
    label: mitochondrial matrix
  evidence_type: IDA
  original_reference_id: PMID:27499294
  qualifier: located_in
  review:
    summary: >-
      Proposed refinement of the existing mitochondrion / mitochondrial-membrane localization:
      COQ8A (and yeast Coq8p) localize to the matrix face of the inner mitochondrial membrane, the
      site of CoQ production. Added to make the core-function localization explicit.
    action: NEW
    supported_by:
    - reference_id: PMID:27499294
      supporting_text: localize to the matrix face of the inner mitochondrial membrane
- term:
    id: GO:0032991
    label: protein-containing complex
  evidence_type: IPI
  original_reference_id: PMID:27499294
  qualifier: part_of
  review:
    summary: >-
      Proposed annotation capturing COQ8A's membership in the multi-subunit CoQ biosynthetic complex
      (COQ synthome / complex Q; COQ3-COQ7, COQ9), which it stabilizes. Recorded via the generic
      protein-containing complex term as no specific COQ synthome term currently exists.
    action: NEW
    supported_by:
    - reference_id: file:human/COQ8A/COQ8A-uniprot.txt
      supporting_text: composed of at least COQ3, COQ4, COQ5, COQ6, COQ7 and COQ9
    - reference_id: PMID:27499294
      supporting_text: Coq8p and COQ8A specifically maintain complex Q
references:
- id: GO_REF:0000024
  title: Manual transfer of experimentally-verified manual GO annotation data to orthologs
    by curator judgment of sequence similarity
  findings: []
- id: GO_REF:0000033
  title: Annotation inferences using phylogenetic trees
  findings: []
- id: GO_REF:0000041
  title: Gene Ontology annotation based on UniPathway vocabulary mapping
  findings: []
- id: GO_REF:0000044
  title: Gene Ontology annotation based on UniProtKB/Swiss-Prot Subcellular Location
    vocabulary mapping, accompanied by conservative changes to GO terms applied by
    UniProt
  findings: []
- id: GO_REF:0000052
  title: Gene Ontology annotation based on curation of immunofluorescence data
  findings: []
- id: PMID:11888884
  title: Isolation of a novel gene, CABC1, encoding a mitochondrial protein that is
    highly homologous to yeast activity of bc1 complex.
  findings: []
  reference_review:
    relevance: MEDIUM
    correctness: VERIFIED
    review_notes: >-
      Original isolation of CABC1/COQ8A; establishes mitochondrial localization and p53
      inducibility. Cached entry is abstract-only (full_text_available: false), but the localization
      and p53-induction claims are corroborated by the UniProt record.
- id: PMID:16189514
  title: Towards a proteome-scale map of the human protein-protein interaction network.
  findings: []
  reference_review:
    relevance: LOW
    correctness: VERIFIED
    review_notes: >-
      Large-scale interactome screen; source of a bare protein-binding IPI. Abstract-only; does not
      inform specific COQ8A molecular function.
- id: PMID:25416956
  title: A proteome-scale map of the human interactome network.
  findings: []
  reference_review:
    relevance: LOW
    correctness: VERIFIED
    review_notes: >-
      Proteome-scale interactome map (source of bare protein-binding IPI entries). Not specific to
      COQ8A function.
- id: PMID:25498144
  title: Mitochondrial ADCK3 employs an atypical protein kinase-like fold to enable
    coenzyme Q biosynthesis.
  findings: []
  reference_review:
    relevance: HIGH
    correctness: VERIFIED
    review_notes: >-
      Crystal structure of ADCK3/COQ8A; defines the atypical PKL fold, the KxGQ domain and A-rich
      (AAAS) loop, the unusual ADP-over-ATP selectivity, and structure-function links to CoQ
      biosynthesis. Full text verified; supporting quotes are verbatim from the cached full text.
- id: PMID:25910212
  title: Widespread macromolecular interaction perturbations in human genetic disorders.
  findings: []
  reference_review:
    relevance: LOW
    correctness: VERIFIED
    review_notes: >-
      Interactome-perturbation study; source of bare protein-binding IPI entries not specific to
      COQ8A function.
- id: PMID:27499294
  title: Cerebellar Ataxia and Coenzyme Q Deficiency through Loss of Unorthodox Kinase
    Activity.
  findings: []
  reference_review:
    relevance: HIGH
    correctness: VERIFIED
    review_notes: >-
      Key functional paper: Coq8a-/- mouse recapitulates ARCA2; demonstrates COQ8 lacks canonical
      protein kinase activity in trans and instead has ATPase activity, binds lipid CoQ
      intermediates, and stabilizes complex Q. Basis for the NOT protein-kinase / NOT
      protein-phosphorylation annotations and the ATPase MF. Full text verified.
- id: PMID:27499296
  title: Mitochondrial Protein Interaction Mapping Identifies Regulators of Respiratory
    Chain Function.
  findings: []
  reference_review:
    relevance: HIGH
    correctness: VERIFIED
    review_notes: >-
      Mitochondrial interaction mapping defining complex Q; the COQ8A IPI partner here is COQ9, a
      bona fide complex-Q member. Supports COQ synthome membership. Full text verified.
- id: PMID:31515488
  title: Extensive disruption of protein interactions by genetic variants across the
    allele frequency spectrum in human populations.
  findings: []
  reference_review:
    relevance: LOW
    correctness: VERIFIED
    review_notes: >-
      Variant-interaction disruption screen; source of bare protein-binding IPI entries not
      specific to COQ8A function.
- id: PMID:32296183
  title: A reference map of the human binary protein interactome.
  findings: []
  reference_review:
    relevance: LOW
    correctness: VERIFIED
    review_notes: >-
      HuRI binary interactome reference map; source of many low-specificity bare protein-binding IPI
      entries not specific to COQ8A function.
- id: PMID:32814053
  title: Interactome Mapping Provides a Network of Neurodegenerative Disease Proteins
    and Uncovers Widespread Protein Aggregation in Affected Brains.
  findings: []
  reference_review:
    relevance: LOW
    correctness: VERIFIED
    review_notes: >-
      Neurodegenerative-disease interactome map; source of bare protein-binding IPI entries.
      Abstract-only cache; not specific to COQ8A molecular function.
- id: PMID:33988507
  title: A subcellular map of the human kinome.
  findings: []
  reference_review:
    relevance: MEDIUM
    correctness: VERIFIED
    review_notes: >-
      Systematic subcellular kinome mapping; assigns COQ8A/ADCK3 to mitochondria. The cached full
      text does not name COQ8A/ADCK3 in prose (large dataset paper), so no verbatim gene-level quote
      is provided; localization is consistent with all other evidence.
- id: PMID:34800366
  title: Quantitative high-confidence human mitochondrial proteome and its dynamics
    in cellular context.
  findings: []
  reference_review:
    relevance: MEDIUM
    correctness: VERIFIED
    review_notes: >-
      High-confidence mitochondrial proteome; supports mitochondrial localization (HTP).
- id: PMID:38425362
  title: In vitro construction of the COQ metabolon unveils the molecular determinants
    of coenzyme Q biosynthesis.
  findings: []
  reference_review:
    relevance: HIGH
    correctness: VERIFIED
    review_notes: >-
      In-vitro reconstitution of the animal COQ metabolon; shows COQ8 increases and streamlines CoQ
      production. Note the experimentally characterized paralog was ancestral COQ8B (recombinant
      COQ8A gave low yields), but the CoQ-biosynthesis role is shared across the COQ8 clade, so the
      GOA IDA attributed to COQ8A is appropriate at the process level. Full text verified.
- id: file:human/COQ8A/COQ8A-uniprot.txt
  title: UniProt entry Q8NI60 (COQ8A_HUMAN)
  findings: []
  reference_review:
    relevance: HIGH
    correctness: VERIFIED
    review_notes: >-
      Authoritative UniProt record; source of function, activity-regulation, subunit (complex Q),
      localization, disease (COQ10D4), and domain/motif statements quoted verbatim in this review.
core_functions:
- description: >-
    ATP-binding activity: COQ8A binds adenine nucleotides via its atypical protein-kinase-like
    fold, with an unusual selectivity for ADP over ATP conferred by the alanine-rich (AAAS)
    nucleotide-binding loop. This nucleotide binding is required to relieve autoinhibition and is
    essential for the protein's role in coenzyme Q biosynthesis.
  molecular_function:
    id: GO:0005524
    label: ATP binding
  directly_involved_in:
  - id: GO:0006744
    label: ubiquinone biosynthetic process
  locations:
  - id: GO:0005759
    label: mitochondrial matrix
  supported_by:
  - reference_id: PMID:25498144
    supporting_text: unusual selectivity for binding ADP over ATP
  - reference_id: file:human/COQ8A/COQ8A-uniprot.txt
    supporting_text: Shows an unusual selectivity for binding ADP over ATP
- description: >-
    ATP hydrolysis (ATPase) activity: rather than canonical protein-kinase phosphotransfer, the
    demonstrated catalytic activity of COQ8/COQ8A is ATP hydrolysis (a small-molecule "water
    kinase" activity) that is enhanced by the UbiB-specific KxGQ motif and by coenzyme-Q head-group
    intermediates. Mutations that abolish this activity eliminate CoQ production in vivo, linking
    the ATPase to the endogenous function; canonical protein-kinase activity in trans is not
    exhibited.
  molecular_function:
    id: GO:0016887
    label: ATP hydrolysis activity
  directly_involved_in:
  - id: GO:0006744
    label: ubiquinone biosynthetic process
  locations:
  - id: GO:0005759
    label: mitochondrial matrix
  supported_by:
  - reference_id: PMID:27499294
    supporting_text: 'Instead, COQ8 has ATPase activity'
  - reference_id: PMID:27499294
    supporting_text: Coq8p ATPase activity is enhanced by the UbiB-specific KxGQ motif
- description: >-
    Coenzyme Q (ubiquinone) biosynthesis: COQ8A is essential for CoQ10 biosynthesis, acting as a
    member and stabilizer of the multi-subunit CoQ biosynthetic complex (the COQ synthome / complex
    Q; COQ3-COQ7, COQ9) at the matrix face of the inner mitochondrial membrane. Loss of COQ8A
    destabilizes complex Q and causes CoQ deficiency (ARCA2/COQ10D4).
  molecular_function:
    id: GO:0005524
    label: ATP binding
  directly_involved_in:
  - id: GO:0006744
    label: ubiquinone biosynthetic process
  in_complex:
    id: GO:0032991
    label: protein-containing complex
  locations:
  - id: GO:0005759
    label: mitochondrial matrix
  supported_by:
  - reference_id: file:human/COQ8A/COQ8A-uniprot.txt
    supporting_text: Atypical kinase involved in the biosynthesis of coenzyme Q
  - reference_id: file:human/COQ8A/COQ8A-uniprot.txt
    supporting_text: composed of at least COQ3, COQ4, COQ5, COQ6, COQ7 and COQ9
  - reference_id: PMID:27499294
    supporting_text: Coq8p and COQ8A specifically maintain complex Q
proposed_new_terms:
- proposed_name: coenzyme Q biosynthetic complex (COQ synthome)
  proposed_definition: >-
    A protein-containing complex, located at the matrix face of the mitochondrial inner membrane,
    that carries out head-group modification steps of ubiquinone (coenzyme Q) biosynthesis. In
    humans it comprises COQ3, COQ4, COQ5, COQ6, COQ7 and COQ9, and is stabilized by the atypical
    UbiB-family kinase COQ8A (and its paralog COQ8B).
  justification: >-
    COQ8A's core cellular role is membership in and stabilization of this complex ("complex Q"),
    but there is no specific protein-complex GO term to record it; only the generic GO:0032991
    protein-containing complex is currently available for the in_complex slot.
suggested_questions:
- question: >-
    What is the physiological small-molecule substrate of COQ8A's ATPase / atypical kinase activity
    in vivo - is it truly a "water kinase" (ATPase), a lipid/prenyl-quinone kinase, or does ATP
    hydrolysis primarily power conformational cycling that assembles complex Q?
- question: >-
    Does COQ8A phosphorylate any endogenous target (protein or lipid) under native conditions, given
    that canonical protein-kinase activity in trans is absent and autophosphorylation is only seen
    with engineered A-rich-loop mutants?
suggested_experiments:
- description: >-
    Reconstitute human complex Q with recombinant COQ8A (not only ancestral/COQ8B) and measure
    CoQ-intermediate-stimulated ATPase activity and its dependence on the KxGQ motif and cardiolipin.
- description: >-
    Use activity-based or metabolomic profiling in COQ8A-null cells rescued with catalytically dead
    (D507N) vs KxGQ-mutant vs wild-type COQ8A to distinguish the roles of nucleotide binding,
    ATP hydrolysis, and complex-Q stabilization in CoQ production.