Affinage

COQ8A

Atypical kinase COQ8A, mitochondrial · UniProt Q8NI60

Length
647 aa
Mass
72.0 kDa
Annotated
2026-06-09
35 papers in source corpus 11 papers cited in narrative 11 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

COQ8A (ADCK3) is a mitochondrial UbiB-family atypical kinase-like protein required for coenzyme Q (CoQ10) biosynthesis, functioning as a regulatory hub for the CoQ biosynthetic machinery (PMID:18319074, PMID:18319072, PMID:21296186). It localizes to mitochondrial cristae via an N-terminal signal, where it associates with the CoQ10 biosynthetic complex components Coq3, Coq5, Coq7, and Coq9, and its deficiency reduces cellular CoQ10 content (PMID:26866375). COQ8A promotes phosphorylation of Coq3, Coq5, and Coq7 in a Coq8-dependent manner and maintains the protein stability of CoQ pathway enzymes including COQ5 and COQ7 [PMID:21296186, PMID:bio_10.1101_2025.04.23.650169]. Structurally, it adopts an atypical protein kinase-like fold whose UbiB-specific features—an N-terminal domain occupying the substrate pocket and an A-rich loop—confer unusual selectivity for ADP over ATP that is essential for CoQ production in vivo, while the kinase domain exhibits Mg2+-dependent ATPase activity (PMID:25498144, PMID:25540914). Its enzymatic activity is allosterically stimulated by CoQ precursor lipids: a precursor mimetic binds a conserved domain to increase nucleotide affinity and ATPase activity, establishing feedback regulation by pathway intermediates (PMID:35904798). In Purkinje neurons, cell-autonomous loss of COQ8A causes mitochondrial dysfunction (primarily Complex IV), intracellular calcium dysregulation, and abnormal dendritic arborization that underlie cerebellar ataxia (PMID:36960552). Separately, in endometrial carcinoma cells COQ8A acts as a direct p53 transcriptional target that promotes ferroptosis through transcriptional activation of ALOX15 (PMID:37402867).

Mechanistic history

Synthesis pass · year-by-year structured walk · 9 steps
  1. 2008 High

    Established that the human gene is a functional ortholog of yeast COQ8/bacterial UbiB required for CoQ biosynthesis, mapping disease-relevant missense changes onto a defined biosynthetic role.

    Evidence Yeast complementation and ubiquinone synthesis measurement with mutations introduced at conserved positions

    PMID:18319072 PMID:18319074

    Open questions at the time
    • Did not define the direct biochemical activity of the human protein
    • Did not identify physical substrates or partners
    • Phylogenetic classification as an atypical kinase was inference only
  2. 2011 High

    Resolved whether ADCK3 acts directly on the CoQ machinery by showing Coq3, Coq5, and Coq7 are phosphorylated in a Coq8-dependent manner, framing it as a protein kinase for the biosynthetic complex.

    Evidence Yeast complementation with human ADCK3 plus two-dimensional gel phosphorylation analysis of Coq substrates

    PMID:21296186

    Open questions at the time
    • Did not show ADCK3 directly phosphorylates these substrates in vitro
    • Did not exclude an indirect/scaffolding contribution to phosphorylation
  3. 2014 High

    Explained the paradox of CoQ-essential but canonical-kinase-dead behavior by solving the structure and demonstrating UbiB-specific features that enforce ADP-over-ATP selectivity required for CoQ production.

    Evidence X-ray crystallography with A-rich loop mutagenesis and in vivo CoQ biosynthesis assays; companion biochemical ATPase assay of the recombinant kinase domain

    PMID:25498144 PMID:25540914

    Open questions at the time
    • Physiological phosphoacceptor and catalytic output remained undefined
    • ATPase activity demonstrated without mutagenesis validation in the in vitro study
  4. 2014 Medium

    Identified a structural basis for higher-order assembly by showing the transmembrane helix homodimerizes via a Gly-zipper motif, implicating oligomerization in activity regulation.

    Evidence Computational transmembrane helix modeling validated by an experimental oligomerization assay

    PMID:25216398

    Open questions at the time
    • Functional consequence of dimerization not directly demonstrated
    • Oligomeric state of full-length protein in mitochondria not established
  5. 2016 Medium

    Localized the protein to mitochondrial cristae and tied its physical association with multiple CoQ biosynthetic components to a functional CoQ10 deficiency.

    Evidence Subcellular fractionation/immunofluorescence, CoQ10 quantification, and in vitro pulldown with recombinant Coq3/Coq5/Coq7/Coq9

    PMID:26866375

    Open questions at the time
    • Interactions shown in vitro with recombinant proteins, not endogenous complex stoichiometry
    • Single lab without reciprocal validation
  6. 2022 Medium

    Defined how the pathway feeds back on the enzyme by mapping a CoQ-precursor-mimetic binding site that allosterically raises nucleotide affinity and ATPase activity.

    Evidence NMR and hydrogen-deuterium exchange mass spectrometry with ATPase activity assay using 2-propylphenol

    PMID:35904798

    Open questions at the time
    • Endogenous lipid ligand and physiological concentration range not established
    • Link between allosteric activation and substrate phosphorylation not shown
  7. 2023 High

    Established cell-autonomous causation of cerebellar ataxia by showing Purkinje-neuron-specific loss drives the disease through mitochondrial (Complex IV) dysfunction, calcium dysregulation, and dendritic defects.

    Evidence Purkinje-specific conditional knockout mouse with behavioral, morphological, mitochondrial, and calcium-imaging readouts

    PMID:36960552

    Open questions at the time
    • Mechanistic chain from CoQ loss to Complex IV and calcium phenotypes not fully resolved
    • Whether dendritic defects are primary or secondary to bioenergetic failure unresolved
  8. 2023 Medium

    Placed COQ8A in a tumor-suppressor signaling axis, identifying it as a direct p53 target that promotes ferroptosis via ALOX15 in endometrial carcinoma.

    Evidence Genome-wide CRISPR screen, ChIP-qPCR, luciferase reporter, RT-qPCR and western blotting

    PMID:37402867

    Open questions at the time
    • Mechanistic link between COQ8A's mitochondrial CoQ role and ALOX15 transcription not defined
    • Single lab in a cancer-specific context
  9. 2025 Medium

    Tested a patient-equivalent point mutant in vivo, showing E548K destabilizes COQ8A and lowers COQ5/COQ7 levels, confirming a chaperone-like stabilization role distinct from overt mitochondrial failure.

    Evidence Knock-in mouse with western blotting of CoQ pathway proteins, mitochondrial assays, and behavioral testing (preprint)

    PMID:bio_10.1101_2025.04.23.650169

    Open questions at the time
    • Preprint, not peer-reviewed
    • Why mitochondrial function and tissue architecture remained intact despite reduced pathway proteins is unexplained

Open questions

Synthesis pass · forward-looking unresolved questions
  • The direct in vitro phosphorylation reaction—whether COQ8A itself catalyzes phosphoryl transfer to a defined acceptor or acts primarily as an ADP-selective stabilizing scaffold—remains unresolved.
  • No reconstituted kinase reaction with an identified physiological substrate
  • Mechanistic unification of phosphorylation, protein stabilization, and ATPase activities is lacking

Mechanism profile

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0016787 hydrolase activity 2 GO:0140657 ATP-dependent activity 2 GO:0140096 catalytic activity, acting on a protein 1
Localization
GO:0005739 mitochondrion 2
Pathway
R-HSA-1430728 Metabolism 3
Partners
COQ3COQ5COQ7COQ9

Evidence

Reading pass · 11 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
2008 ADCK3 (COQ8A) is a mitochondrial protein homologous to yeast COQ8 and bacterial UbiB proteins required for CoQ biosynthesis; missense mutations introduced at corresponding yeast COQ8 positions caused respiratory phenotype and severely reduced ubiquinone synthesis, demonstrating these mutations alter protein function in CoQ biosynthesis. Yeast complementation assay, growth on nonfermentable carbon source, ubiquinone synthesis measurement American journal of human genetics High 18319072 18319074
2008 ADCK3 belongs to the family of atypical kinases (including phosphoinositide and choline kinases), suggesting it plays an indirect regulatory role in ubiquinone biosynthesis possibly as part of a feedback loop regulating ATP production. Phylogenetic analysis American journal of human genetics Low 18319074
2011 Human ADCK3 (with a yeast mitochondrial leader sequence) rescues growth of yeast coq8 null mutants on nonfermentable carbon source and partially restores Q6 biosynthesis; furthermore, Coq3p, Coq5p, and Coq7p are phosphorylated in a Coq8p-dependent manner, indicating ADCK3 functions as a protein kinase that phosphorylates CoQ biosynthetic complex components. Yeast complementation, two-dimensional gel phosphorylation analysis, ubiquinone biosynthesis measurement Biochimica et biophysica acta High 21296186
2014 Crystal structure of ADCK3 reveals it employs an atypical protein kinase-like fold with multiple UbiB-specific features that inhibit canonical protein kinase activity: an N-terminal domain occupies the typical substrate binding pocket, and a unique A-rich loop limits ATP binding by establishing unusual selectivity for ADP over ATP. A single alanine-to-glycine mutation in the A-rich loop flips coenzyme selectivity to enable autophosphorylation but inhibits CoQ biosynthesis in vivo, demonstrating the functional relevance of ADP selectivity for CoQ production. X-ray crystallography, site-directed mutagenesis, in vivo CoQ biosynthesis assay, biochemical coenzyme selectivity assay Molecular cell High 25498144
2014 The transmembrane helix of ADCK3 homodimerizes via an extended Gly-zipper motif, as predicted computationally and validated experimentally; this transmembrane domain oligomerization is proposed to regulate ADCK3 biological activity. Computational modeling of transmembrane helix interactions, experimental validation of oligomerization (transmembrane helix association assay) Journal of the American Chemical Society Medium 25216398
2014 Human ADCK3 kinase domain exhibits Mg2+-dependent ATPase activity when expressed as a maltose-binding protein fusion in E. coli, providing direct biochemical evidence for its function as an atypical kinase. Recombinant protein expression, in vitro ATPase activity assay Protein expression and purification Medium 25540914
2016 ADCK3 localizes to mitochondrial cristae via an N-terminal localization signal; ADCK3 deficiency decreases cellular CoQ10 content; endogenous ADCK3 associates in vitro with recombinant Coq3, Coq5, Coq7, and Coq9 (components of the CoQ10 biosynthetic machinery). Subcellular fractionation/immunofluorescence for localization, CoQ10 quantification, in vitro pulldown with recombinant proteins PloS one Medium 26866375
2022 The small molecule 2-propylphenol (a CoQ precursor mimetic) binds COQ8A at an identified site and allosterically modulates a conserved COQ8A domain to increase nucleotide affinity and ATPase activity, revealing a mechanism by which CoQ precursor lipids regulate COQ8A enzymatic function. NMR, hydrogen-deuterium exchange mass spectrometry, ATPase activity assay ACS chemical biology Medium 35904798
2023 Conditional Purkinje-neuron-specific knockout of COQ8A demonstrates that loss of COQ8A specifically in Purkinje neurons is the main cause of cerebellar ataxia; COQ8A-depleted Purkinje neurons exhibit abnormal dendritic arborizations, altered mitochondrial function, and intracellular calcium dysregulation; oxidative phosphorylation (particularly Complex IV) is primarily altered at presymptomatic stages. Purkinje-specific conditional knockout mouse, behavioral/motor testing, in vivo and in vitro morphological analysis, mitochondrial function assays, calcium imaging Brain : a journal of neurology High 36960552
2023 ADCK3 is a direct transcriptional target of tumor suppressor p53 in endometrial carcinoma cells; loss of ADCK3 suppresses MPA-mediated ferroptosis by abrogating ALOX15 transcriptional activation, placing ADCK3 downstream of p53 and upstream of ALOX15 in a ferroptosis pathway. Genome-wide CRISPR screen, ChIP-qPCR, luciferase reporter assay, western blotting, RT-qPCR British journal of cancer Medium 37402867
2025 The COQ8A E548K (equivalent to human E551K) knock-in mutation in mice leads to variable instability of the COQ8A E548K protein and reduced expression of COQ5 and COQ7 in cerebellum and muscle (similar to constitutive knockout), demonstrating that COQ8A is required for maintaining protein levels of other CoQ biosynthesis pathway components; however, mitochondrial function and tissue architecture remained intact in the knock-in model. Knock-in mouse model, western blotting of CoQ pathway proteins, mitochondrial function assays, behavioral testing bioRxivpreprint Medium bio_10.1101_2025.04.23.650169

Source papers

Stage 0 corpus · 35 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
2008 ADCK3, an ancestral kinase, is mutated in a form of recessive ataxia associated with coenzyme Q10 deficiency. American journal of human genetics 243 18319074
2008 CABC1 gene mutations cause ubiquinone deficiency with cerebellar ataxia and seizures. American journal of human genetics 217 18319072
2014 Mitochondrial ADCK3 employs an atypical protein kinase-like fold to enable coenzyme Q biosynthesis. Molecular cell 100 25498144
2011 Expression of the human atypical kinase ADCK3 rescues coenzyme Q biosynthesis and phosphorylation of Coq polypeptides in yeast coq8 mutants. Biochimica et biophysica acta 96 21296186
2011 Adult-onset cerebellar ataxia due to mutations in CABC1/ADCK3. Journal of neurology, neurosurgery, and psychiatry 86 22036850
2020 Clinico-Genetic, Imaging and Molecular Delineation of COQ8A-Ataxia: A Multicenter Study of 59 Patients. Annals of neurology 64 32337771
2010 Nonsense mutations in CABC1/ADCK3 cause progressive cerebellar ataxia and atrophy. Mitochondrion 60 20580948
2002 Isolation of a novel gene, CABC1, encoding a mitochondrial protein that is highly homologous to yeast activity of bc1 complex. Cancer research 44 11888884
2013 Autosomal-recessive cerebellar ataxia caused by a novel ADCK3 mutation that elongates the protein: clinical, genetic and biochemical characterisation. Journal of neurology, neurosurgery, and psychiatry 41 24218524
2016 Cerebellar ataxia and severe muscle CoQ10 deficiency in a patient with a novel mutation in ADCK3. Clinical genetics 39 26818466
2013 Heterozygous Mutations in the ADCK3 Gene in Siblings with Cerebellar Atrophy and Extreme Phenotypic Variability. JIMD reports 35 24048965
2018 ADCK3-related Coenzyme Q10 Deficiency: A Potentially Treatable Genetic Disease. Movement disorders clinical practice 31 30637285
2019 Dystonia-Ataxia with early handwriting deterioration in COQ8A mutation carriers: A case series and literature review. Parkinsonism & related disorders 25 31621627
2020 Primary coenzyme Q10 deficiency due to COQ8A gene mutations. Molecular genetics & genomic medicine 22 32743982
2023 Mitochondrial dysfunction and calcium dysregulation in COQ8A-ataxia Purkinje neurons are rescued by CoQ10 treatment. Brain : a journal of neurology 21 36960552
2016 AarF Domain Containing Kinase 3 (ADCK3) Mutant Cells Display Signs of Oxidative Stress, Defects in Mitochondrial Homeostasis and Lysosomal Accumulation. PloS one 21 26866375
2019 Primary Coenzyme Q deficiency Due to Novel ADCK3 Variants, Studies in Fibroblasts and Review of Literature. Neurochemical research 18 30968303
2014 A Gly-zipper motif mediates homodimerization of the transmembrane domain of the mitochondrial kinase ADCK3. Journal of the American Chemical Society 18 25216398
2019 One-year outcome of coenzyme Q10 supplementation in ADCK3 ataxia (ARCA2). Cerebellum & ataxias 15 31890231
2018 COQ8A and MED25 Mutations in a Child with Intellectual Disability, Microcephaly, Seizures, and Spastic Ataxia: Synergistic Effect of Digenic Variants? Molecular syndromology 11 30800049
2014 Preparation and characterization of human ADCK3, a putative atypical kinase. Protein expression and purification 11 25540914
2023 Genome-wide CRISPR screening reveals ADCK3 as a key regulator in sensitizing endometrial carcinoma cells to MPA therapy. British journal of cancer 9 37402867
2022 Epilepsia Partialis Continua a Clinical Feature of a Missense Variant in the ADCK3 Gene and Poor Response to Therapy. Journal of molecular neuroscience : MN 9 35275351
2021 Photoparoxysmal response in ADCK3 autosomal recessive ataxia: a case report and literature review. Epileptic disorders : international epilepsy journal with videotape 8 33622667
2023 Adolescence Onset Primary Coenzyme Q10 Deficiency With Rare CoQ8A Gene Mutation: A Case Report and Review of Literature. Clinical medicine insights. Case reports 7 37476682
2019 Exome sequencing found a novel homozygous deletion in ADCK3 gene involved in autosomal recessive spinocerebellar ataxia. Gene 7 31078656
2022 Primary CoQ10 deficiency with a severe phenotype due to the c.901 C > T (p.R301W) mutation in the COQ8A gene. The International journal of neuroscience 6 35757998
2020 A novel COQ8A missense variant associated with a mild form of primary coenzyme Q10 deficiency type 4. Clinical biochemistry 6 32553579
2023 Stroke-Like Episodes and Epilepsy in a Patient with COQ8A-Related Coenzyme Q10 Deficiency. Annals of Indian Academy of Neurology 4 38229639
2016 Correction: AarF Domain Containing Kinase 3 (ADCK3) Mutant Cells Display Signs of Oxidative Stress, Defects in Mitochondrial Homeostasis and Lysosomal Accumulation. PloS one 4 27442024
2024 Mitochondrial Dysfunction due to Novel COQ8A Variation with Poor Response to CoQ10 Treatment: A Comprehensive Study and Review of Literatures. Cerebellum (London, England) 3 38429489
2022 2-Propylphenol Allosterically Modulates COQ8A to Enhance ATPase Activity. ACS chemical biology 2 35904798
2024 Identification of Potent ADCK3 Inhibitors through Structure-Based Virtual Screening. Journal of chemical information and modeling 1 39025788
2026 Case Report: Myoclonic and tremulous movements associated with COQ8A-related coenzyme Q10 deficiency type 4. Frontiers in genetics 0 41568333
2026 COQ8A-related Primary Coenzyme Q10 Deficiency Mimicking Mitochondrial Encephalomyopathy, Lactic Acidosis, and Stroke-like Syndrome: A Pediatric Case Report and Review of Mitochondrial Mimics. Annals of African medicine 0 41992454

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