{"gene":"COQ7","run_date":"2026-06-09T22:57:19","timeline":{"discoveries":[{"year":1997,"finding":"CLK-1 (C. elegans) is structurally and functionally conserved with yeast Cat5p/Coq7p; clk-1 complemented cat5/coq7 null mutants in yeast, demonstrating shared biochemical function in ubiquinone biosynthesis.","method":"Genetic complementation of yeast coq7/cat5 null mutants by clk-1; sequence homology analysis","journal":"Science","confidence":"High","confidence_rationale":"Tier 1 / Strong — functional complementation across species with direct phenotypic rescue, replicated conceptually in multiple subsequent studies","pmids":["9020081"],"is_preprint":false},{"year":1996,"finding":"Yeast COQ7 is required for ubiquinone biosynthesis; coq7 mutants lack ubiquinone but accumulate demethoxyubiquinone (DMQ), placing COQ7 at a hydroxylase step converting DMQ to ubiquinone.","method":"Genetic deletion and complementation in S. cerevisiae; lipid analysis by HPLC; growth assay on nonfermentable carbon sources","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro biochemical analysis and genetic deletion with rescue, independently replicated across organisms","pmids":["8621692"],"is_preprint":false},{"year":1998,"finding":"Yeast Coq7p/Cat5p is localized to the mitochondrial inner membrane and is directly involved in ubiquinone biosynthesis; the defect in gluconeogenic gene activation in coq7/cat5 null mutants is a secondary consequence of impaired respiration, not a direct transcriptional function.","method":"Subcellular fractionation; mitochondrial localization assay; genetic epistasis with respiration-defective mutants","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Strong — direct localization with functional consequence, epistasis resolving two proposed functions, replicated across labs","pmids":["9452453"],"is_preprint":false},{"year":1999,"finding":"C. elegans CLK-1 fused to GFP is fully active and localizes to mitochondria in all somatic cells; overexpression of CLK-1 increases mitochondrial activity and accelerates behavioral rates while shortening lifespan, demonstrating a regulatory role in mitochondrial function and aging.","method":"GFP fusion protein live imaging; mitochondrial dye-uptake assay in vivo; succinate cytochrome c reductase assay in vitro; transgenic overexpression","journal":"The EMBO journal","confidence":"High","confidence_rationale":"Tier 2 / Strong — direct subcellular localization tied to functional consequence, multiple orthogonal methods, overexpression phenotype","pmids":["10202142"],"is_preprint":false},{"year":2001,"finding":"CLK-1 is absolutely required for ubiquinone (UQ9) biosynthesis in C. elegans; clk-1 mutants lack UQ9 and instead accumulate DMQ9, which can partially substitute as an electron carrier in the respiratory chain.","method":"Lipid extraction and HPLC analysis of quinone species; mitochondrial respiratory enzyme activity assays (NADH-cytochrome c reductase, succinate-cytochrome c reductase); chemical synthesis of DMQ2 and functional assay","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — direct biochemical identification of substrate accumulation and enzymatic bypass, multiple orthogonal methods","pmids":["11244089"],"is_preprint":false},{"year":2001,"finding":"COQ7 belongs to the di-iron carboxylate oxidase/hydroxylase family based on a conserved iron-ligand sequence motif; bacterial COQ7 homologs from P. aeruginosa and T. ferrooxidans complement an E. coli mutant lacking the 5-demethoxyubiquinone hydroxylase, confirming direct hydroxylase function.","method":"Sequence analysis; cloning of bacterial COQ7 homologs; functional complementation of E. coli ubiB mutant; structural modeling","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — functional complementation with structural inference; single lab, no direct iron measurement","pmids":["11435415"],"is_preprint":false},{"year":2001,"finding":"Mouse COQ7 (mCLK1) is synthesized as a preprotein, imported into the mitochondrial matrix where the leader sequence is cleaved, and becomes loosely associated with the inner membrane; unusually, this import does not require mitochondrial membrane potential.","method":"Subcellular fractionation; protease protection assay; import assay with membrane potential uncouplers; immunoblotting of processed vs. precursor forms","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Strong — direct import assay with mutagenesis of targeting sequence and membrane potential manipulation, multiple orthogonal approaches","pmids":["11387338"],"is_preprint":false},{"year":2001,"finding":"Mouse COQ7 is essential for CoQ9 synthesis; COQ7-deficient mouse embryos fail to synthesize CoQ9 and instead accumulate DMQ9; COQ7 deficiency causes mitochondrial structural abnormalities (enlarged mitochondria with vesicular cristae) and embryonic lethality at E10.5.","method":"Targeted gene disruption (knockout mouse); biochemical CoQ analysis; electron microscopy; cell culture rescue experiments","journal":"Biochemical and biophysical research communications","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic knockout with biochemical phenotype (CoQ analysis), structural (EM), and rescue experiments","pmids":["11716496"],"is_preprint":false},{"year":2001,"finding":"The maternal rescue phenotype of C. elegans clk-1 mutants is explained by persistence of small amounts of maternally provided CLK-1 protein, which is sufficient for synthesis of considerable ubiquinone during early development; gradual depletion of CLK-1 and ubiquinone drives expression of mutant phenotype.","method":"Western blotting for CLK-1 protein levels; ubiquinone measurement; developmental arrest experiments; double mutant analysis (daf-2 clk-1)","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — biochemical demonstration of protein persistence linked to UQ levels, single lab","pmids":["14517217"],"is_preprint":false},{"year":2002,"finding":"C. elegans CLK-1 and mouse CLK-1 have DNA-binding activity specific to the OL (light-strand origin of replication) region of mitochondrial DNA; this activity is inhibited by ADP and is altered by life-span-extending clk-1 mutations.","method":"Electrophoretic mobility shift assay (EMSA); competition binding with specific vs. nonspecific DNA; ADP inhibition assay; mutant vs. wild-type protein comparison","journal":"FEBS letters","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single lab, single method (EMSA), not independently replicated; functional significance not established","pmids":["11959146"],"is_preprint":false},{"year":2003,"finding":"C. elegans CLK-1 functions as a demethoxyubiquinone (DMQ) hydroxylase; complementation of E. coli ubiF mutants by C. elegans CLK-1 demonstrated that the eukaryotic CLK-1/Coq7 family can directly catalyze the hydroxylation of DMQ to produce hydroxyubiquinone.","method":"Functional complementation of E. coli ubiF mutant; growth on nonfermentable carbon source; ubiquinone synthesis assay","journal":"FEBS letters","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — functional complementation across kingdoms demonstrating enzymatic activity, single lab","pmids":["12753928"],"is_preprint":false},{"year":2006,"finding":"Yeast Coq7p co-migrates with Coq3p and Coq4p as a high-molecular-mass complex; Coq7p (and the quinone lipids DMQ and Q) function to stabilize other Coq polypeptides; E. coli UbiF can substitute for the hydroxylase activity of Coq7p but the structural/stabilization role requires Coq7p itself.","method":"Complementation of coq7 point and null mutants by UbiF; gel filtration co-migration analysis; immunoblotting for Coq3, Coq4, Coq6 levels; addition of exogenous Q to null mutant","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple biochemical methods distinguishing enzymatic vs. structural roles, single lab","pmids":["16624818"],"is_preprint":false},{"year":2008,"finding":"Clioquinol (a metal chelator) inhibits mammalian CLK-1 (COQ7) enzymatic activity in cultured cells; this inhibition is blocked by iron or cobalt cations, indicating chelation of the active-site metal is the mechanism of action.","method":"Cell-based CLK-1 activity assay; metal cation rescue experiments (iron, cobalt); phenotypic comparison of clioquinol-treated vs. clk-1 mutant nematodes and mice","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — cell-based enzymatic assay with metal rescue, phenotypic confirmation in two organisms, single lab","pmids":["18927074"],"is_preprint":false},{"year":2010,"finding":"Mouse CLK-1 (MCLK1) is a di-iron carboxylate protein; Mössbauer and EPR spectroscopy confirmed iron binding; in vitro activity assays showed NADH can serve directly as reductant for the diiron center to activate dioxygen and catalyze substrate oxidation, with no requirement for an additional reductase protein.","method":"Heterologous expression in E. coli; Mössbauer spectroscopy; EPR spectroscopy; in vitro enzyme activity assay with quinone substrates and NADH","journal":"Biochemistry","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro reconstitution with spectroscopic characterization and substrate assay, multiple orthogonal methods in one study","pmids":["20923139"],"is_preprint":false},{"year":2013,"finding":"The mitochondrial Ser/Thr phosphatase Ptc7p activates CoQ6 biosynthesis in yeast by dephosphorylating Coq7p; phosphorylated Coq7p is inactive, and Ptc7p-mediated dephosphorylation is required for Coq7p hydroxylase activity.","method":"Genetic deletion of PTC7; CoQ6 measurement by HPLC; phosphorylation analysis; epistasis experiments; aerobic growth assays","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic and biochemical evidence for phosphoregulation of Coq7p, single lab with multiple methods","pmids":["23940037"],"is_preprint":false},{"year":2014,"finding":"COQ9 specifically interacts with COQ7 through conserved residues in mammals; COQ9 has a lipid-binding site and associates with multiple lipid species including CoQ itself; the COQ9 residues necessary for COQ7 interaction form a surface patch around the lipid-binding site, suggesting COQ9 presents its bound lipid substrate to COQ7.","method":"Crystal structure of human COQ9 at 2.4 Å; Co-IP/pulldown of COQ9-COQ7 interaction; MS-based lipid identification; disease-associated mouse model with COQ9 mutation showing disrupted CoQ protein complex; mutagenesis of conserved residues","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structure plus biochemical interaction mapping plus mouse disease model, multiple orthogonal methods","pmids":["25339443"],"is_preprint":false},{"year":2015,"finding":"A nuclear form of CLK-1 exists in C. elegans (and is conserved to humans) that independently regulates lifespan through a retrograde signaling pathway responsive to mitochondrial ROS; nuclear CLK-1 modulates gene expression to regulate mitochondrial ROS metabolism and the mitochondrial unfolded protein response.","method":"Subcellular fractionation; fluorescence imaging of tagged CLK-1; genetic epistasis with ROS pathway mutants; gene expression analysis; lifespan assays with nuclear-localized CLK-1 constructs","journal":"Nature cell biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct localization experiments plus functional consequence on lifespan and gene expression, single lab; contradicted by PMID 28404998 which did not detect nuclear enrichment","pmids":["25961505"],"is_preprint":false},{"year":2015,"finding":"The RNA-binding protein HuR stabilizes COQ7 mRNA via binding to the 3'-UTR (first 765 bp); HuR knockdown or serum deprivation destabilizes COQ7 mRNA, reduces COQ7 protein levels, decreases CoQ biosynthesis, reduces oxygen consumption and ATP production, and increases glycolysis.","method":"RNA-binding protein pulldown (RIP); mRNA stability assay (half-life measurement); siRNA knockdown of HuR and hnRNP C1/C2; oxygen consumption rate (Seahorse); ATP and lactate measurements","journal":"RNA biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct RBP-mRNA interaction assay with functional metabolic readouts, multiple methods, single lab","pmids":["26690054"],"is_preprint":false},{"year":2015,"finding":"A homozygous COQ7 missense mutation (V141E) in a human patient causes primary CoQ deficiency; 2,4-dihydroxybenzoic acid (2,4-DHB), which bypasses the COQ7 enzymatic step, rescues CoQ levels and biochemical defects in patient fibroblasts.","method":"Whole exome sequencing; CoQ measurement by UPLC-MS in patient fibroblasts; rescue with 2,4-DHB; functional mitochondrial assays","journal":"Journal of medical genetics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — biochemical demonstration of enzyme loss with substrate bypass rescue in patient cells, single lab","pmids":["26084283"],"is_preprint":false},{"year":2017,"finding":"All pleiotropic phenotypes of C. elegans clk-1 null mutants (behavioral, developmental, mitochondrial quality control gene expression, lifespan) are attributable to loss of ubiquinone biosynthesis; pharmacological restoration of UQ biosynthesis rescues all phenotypes; no nuclear enrichment of MCLK1 or CLK-1 was detected in worms or mammalian cell fractionation.","method":"Immunohistochemistry in C. elegans; subcellular fractionation in mammalian cells; pharmacological UQ restoration; lifespan analysis; gene expression analysis; CLK-1 constructs lacking mitochondrial targeting sequence","journal":"Scientific reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal methods resolving single-function vs. multi-function debate, single lab; directly contradicts nuclear localization claim","pmids":["28404998"],"is_preprint":false},{"year":2022,"finding":"COQ7 adopts a ferritin-like (di-iron carboxylate) fold with a hydrophobic channel whose substrate-binding capacity is enhanced by COQ9; two COQ7:COQ9 heterodimers form a curved tetramer that deforms the mitochondrial inner membrane, potentially allowing CoQ intermediates to translocate from the bilayer to the proteins' lipid-binding sites; two tetramers assemble into a soluble octamer with a pseudo-bilayer of lipids captured within.","method":"Cryo-EM structure of COQ7:COQ9 complex with bound lipid/substrate/NADH; molecular dynamics simulations; structure-function mutagenesis","journal":"Molecular cell","confidence":"High","confidence_rationale":"Tier 1 / Strong — cryo-EM structure with functional validation and molecular dynamics, multiple orthogonal methods in one study","pmids":["36306796"],"is_preprint":false},{"year":2022,"finding":"Manganese exposure inhibits COQ7 di-iron carboxylate hydroxylase activity in mouse cells; pre-treatment with cobalt interferes with manganese inhibition, suggesting cobalt has greater affinity than both iron and manganese for the COQ7 active site and maintains catalytic activity when substituted.","method":"Cell-based COQ7 activity assay (CoQ biosynthesis measurement); manganese and cobalt treatment; competitive metal replacement assay","journal":"microPublication biology","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single cell-based assay, single lab, no direct metal occupancy measurement","pmids":["36176269"],"is_preprint":false}],"current_model":"COQ7 (CLK-1) is a mitochondrial di-iron carboxylate hydroxylase that catalyzes the penultimate step of coenzyme Q (ubiquinone) biosynthesis—the hydroxylation of 5-demethoxyubiquinone (DMQ)—using NADH directly as a reductant; it forms a functional complex with the lipid-binding protein COQ9, which presents the hydrophobic CoQ intermediate to COQ7's active site within a membrane-deforming COQ7:COQ9 tetramer, and its hydroxylase activity is post-translationally regulated by dephosphorylation (via Ptc7p in yeast) and by active-site metal occupancy; loss of COQ7 function causes accumulation of DMQ, depletion of CoQ, mitochondrial respiratory failure, and in mammals, embryonic lethality or inherited neurological disease."},"narrative":{"mechanistic_narrative":"COQ7 (CLK-1) is the mitochondrial di-iron carboxylate hydroxylase that catalyzes a penultimate step of coenzyme Q (ubiquinone) biosynthesis, converting 5-demethoxyubiquinone (DMQ) to the hydroxylated intermediate en route to mature CoQ [PMID:8621692, PMID:11435415, PMID:20923139]. Its requirement for ubiquinone synthesis is deeply conserved: yeast Coq7p, C. elegans CLK-1, and mouse COQ7 are functionally interchangeable, and loss of the enzyme in any of these systems blocks CoQ production and causes accumulation of the DMQ precursor [PMID:9020081, PMID:8621692, PMID:11244089, PMID:11716496]. The protein is imported into the mitochondrial matrix and associates with the inner membrane, where it operates [PMID:9452453, PMID:11387338]. Biochemically, COQ7 carries a ferritin-like di-iron carboxylate center that, with NADH serving directly as the reductant, activates dioxygen for substrate oxidation without a separate reductase, and its activity depends on active-site metal occupancy—chelation by clioquinol abolishes activity in a manner reversed by iron or cobalt [PMID:18927074, PMID:20923139]. COQ7 functions in a complex with the lipid-binding protein COQ9: COQ9 presents its bound hydrophobic CoQ intermediate to the COQ7 active site, and two COQ7:COQ9 heterodimers form a curved, membrane-deforming tetramer (assembling further into a lipid-containing octamer) that extracts CoQ intermediates from the bilayer for catalysis [PMID:25339443, PMID:36306796]. The enzyme is regulated post-translationally by phosphorylation, with the mitochondrial phosphatase Ptc7p dephosphorylating and thereby activating yeast Coq7p [PMID:23940037], and at the mRNA level through stabilization of COQ7 transcript by the RNA-binding protein HuR [PMID:26690054]. Because CoQ is essential for respiration, loss of COQ7 produces mitochondrial respiratory failure, abnormal mitochondrial structure, and embryonic lethality in mouse, and a homozygous COQ7 missense mutation (V141E) causes primary CoQ deficiency disease in humans, rescuable by the bypass metabolite 2,4-dihydroxybenzoic acid [PMID:11716496, PMID:26084283]. The pleiotropic developmental, behavioral, and lifespan phenotypes of clk-1 mutants in C. elegans are attributable to loss of ubiquinone biosynthesis [PMID:28404998].","teleology":[{"year":1996,"claim":"Established that COQ7 acts at a defined hydroxylase step of ubiquinone biosynthesis by showing its loss blocks CoQ and causes accumulation of the DMQ precursor.","evidence":"Genetic deletion/complementation in S. cerevisiae with HPLC lipid analysis and nonfermentable growth assays","pmids":["8621692"],"confidence":"High","gaps":["Did not directly demonstrate enzymatic chemistry or the catalytic cofactor","Substrate-presentation and partner requirements unknown"]},{"year":1997,"claim":"Demonstrated deep evolutionary conservation of COQ7 function by showing C. elegans clk-1 rescues yeast coq7/cat5 nulls, unifying the gene's role across species.","evidence":"Cross-species genetic complementation and sequence homology analysis","pmids":["9020081"],"confidence":"High","gaps":["Conservation of function did not define molecular mechanism","Catalytic identity still inferential"]},{"year":1998,"claim":"Resolved competing functional models by localizing Coq7p to the mitochondrial inner membrane and showing its apparent transcriptional/gluconeogenic role is secondary to respiratory failure.","evidence":"Subcellular fractionation and genetic epistasis with respiration-defective mutants","pmids":["9452453"],"confidence":"High","gaps":["Did not establish enzymatic mechanism","Membrane association mode not detailed"]},{"year":2001,"claim":"Defined COQ7 as a di-iron carboxylate hydroxylase and confirmed its direct enzymatic activity through bacterial homolog complementation, while characterizing its mitochondrial import and the consequences of its loss in metazoans.","evidence":"Sequence/structural analysis with E. coli ubiB complementation; import/protease-protection assays; mouse knockout with CoQ analysis and EM; C. elegans quinone HPLC and respiratory assays","pmids":["11435415","11387338","11716496","11244089"],"confidence":"High","gaps":["Direct iron measurement not yet performed","Identity of the in vivo reductant unresolved","How DMQ reaches the active site unknown"]},{"year":2003,"claim":"Confirmed that the eukaryotic CLK-1/Coq7 family directly catalyzes DMQ hydroxylation, cementing its enzymatic assignment.","evidence":"Complementation of E. coli ubiF mutant with growth and ubiquinone synthesis readouts","pmids":["12753928"],"confidence":"Medium","gaps":["Single lab; no purified enzyme kinetics","Cofactor chemistry not directly probed"]},{"year":2006,"claim":"Separated COQ7's catalytic role from a structural role, showing it (with quinone lipids) stabilizes other Coq polypeptides within a high-molecular-mass biosynthetic complex independent of its hydroxylase chemistry.","evidence":"UbiF complementation, gel filtration co-migration, and immunoblotting of Coq3/Coq4/Coq6 in yeast","pmids":["16624818"],"confidence":"Medium","gaps":["Stoichiometry and architecture of the complex undefined","Mechanism of polypeptide stabilization unclear"]},{"year":2010,"claim":"Directly proved the di-iron center and showed NADH can serve as the reductant without an accessory reductase, defining the core catalytic mechanism.","evidence":"E. coli expression, Mössbauer and EPR spectroscopy, and in vitro activity assays with quinone substrates and NADH","pmids":["20923139"],"confidence":"High","gaps":["Physiological reductant in vivo not confirmed","Structural basis of substrate access not yet resolved"]},{"year":2013,"claim":"Identified post-translational regulation of COQ7 activity, showing phosphorylated Coq7p is inactive and the phosphatase Ptc7p activates it by dephosphorylation.","evidence":"PTC7 deletion, CoQ6 HPLC, phosphorylation analysis, and epistasis/aerobic growth assays in yeast","pmids":["23940037"],"confidence":"Medium","gaps":["Phospho-sites and kinase not fully mapped","Conservation of phosphoregulation in mammals not established here"]},{"year":2014,"claim":"Established the molecular basis of COQ7-COQ9 partnership, showing COQ9 binds lipids/CoQ and presents substrate to COQ7 via a defined surface patch.","evidence":"Crystal structure of human COQ9, Co-IP/pulldown, MS lipid identification, mutagenesis, and a disease mouse model","pmids":["25339443"],"confidence":"High","gaps":["Did not yet visualize the assembled COQ7:COQ9 complex","Mechanism of lipid handoff inferred not observed"]},{"year":2015,"claim":"Extended COQ7 regulation to the transcript level and linked it to human disease, while a contested report proposed a nuclear retrograde-signaling form.","evidence":"HuR RIP/mRNA stability with metabolic readouts; patient WES with 2,4-DHB bypass rescue in fibroblasts; subcellular fractionation/lifespan assays for the nuclear-CLK-1 claim","pmids":["26690054","26084283","25961505"],"confidence":"Medium","gaps":["Nuclear localization was not detected in a subsequent study (PMID 28404998)","Generality of HuR regulation across tissues unknown","Single patient for the disease allele"]},{"year":2017,"claim":"Argued that all pleiotropic clk-1 phenotypes derive from loss of ubiquinone biosynthesis and found no nuclear enrichment, directly challenging a separate nuclear-signaling function.","evidence":"Immunohistochemistry, mammalian fractionation, pharmacological UQ restoration, and lifespan/gene-expression analysis","pmids":["28404998"],"confidence":"Medium","gaps":["Single lab; reconciliation with nuclear-CLK-1 report unresolved","Does not exclude minor non-canonical pools"]},{"year":2022,"claim":"Provided the structural mechanism of catalysis-in-membrane, showing COQ7:COQ9 heterodimers form a curved tetramer that deforms the inner membrane to extract CoQ intermediates, and refined understanding of active-site metal selectivity.","evidence":"Cryo-EM of the COQ7:COQ9 complex with bound lipid/substrate/NADH plus molecular dynamics and mutagenesis; cell-based activity assays with manganese/cobalt metal competition","pmids":["36306796","36176269"],"confidence":"High","gaps":["In vivo relevance of the soluble octamer not established","Metal-occupancy regulation (Mn/Co) rests on single low-confidence cell assay without direct occupancy measurement"]},{"year":null,"claim":"How COQ7 activity is integrated across phosphoregulation, metal occupancy, membrane-deformation dynamics, and tissue-specific regulation to control CoQ output in mammals remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["Mammalian phosphoregulation circuitry undefined","In vivo physiological reductant and metal-loading control unconfirmed","Spectrum of human COQ7 disease alleles and genotype-phenotype relationships incomplete"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0016491","term_label":"oxidoreductase activity","supporting_discovery_ids":[1,5,10,13]},{"term_id":"GO:0016787","term_label":"hydrolase activity","supporting_discovery_ids":[1,5,10]}],"localization":[{"term_id":"GO:0005739","term_label":"mitochondrion","supporting_discovery_ids":[3,6,7]}],"pathway":[{"term_id":"R-HSA-1430728","term_label":"Metabolism","supporting_discovery_ids":[1,4,7]}],"complexes":["COQ7:COQ9 hydroxylase complex","high-molecular-mass CoQ biosynthetic complex (Coq3/Coq4/Coq7)"],"partners":["COQ9","PTC7","ELAVL1 (HUR)"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q99807","full_name":"NADPH-dependent 3-demethoxyubiquinone 3-hydroxylase, mitochondrial","aliases":["3-demethoxyubiquinone 3-hydroxylase (NADH)","Timing protein clk-1 homolog","Ubiquinone biosynthesis monooxygenase COQ7"],"length_aa":217,"mass_kda":24.3,"function":"Catalyzes the hydroxylation of the 5-methoxy-2-methyl-3-(all-trans-polyprenyl)benzoquinone at the C6 position and participates in the biosynthesis of ubiquinone (Probable). Catalyzes the reaction through a substrate-mediated reduction pathway, whereby NADH shuttles electrons to 5-methoxy-2-methyl-3-(all-trans-decaprenyl)benzoquinone, which then transfers the electrons to the two Fe(3+) centers (PubMed:23445365). The binding of 5-methoxy-2-methyl-3-(all-trans-polyprenyl)benzoquinone (DMQn) mediates reduction of the diiron center by nicotinamide adenine dinucleotide (NADH) and initiates oxygen activation for subsequent DMQ hydroxylation (PubMed:23445365). The physiological substrates are 5-methoxy-2-methyl-3-(all-trans-nonaprenyl)benzoquinone (DMQ(9)) and 5-methoxy-2-methyl-3-(all-trans-decaprenyl)benzoquinone (DMQ(10)), however in vitro the enzyme does not have any specificity concerning the length of the polyprenyl tail, and accepts tails of various lengths with similar efficiency (PubMed:23445365, PubMed:28409910). Also has a structural role in the COQ enzyme complex, stabilizing other COQ polypeptides. Involved in lifespan determination in a ubiquinone-independent manner (By similarity). Plays a role in modulating mitochondrial stress responses, acting in the nucleus, perhaps via regulating gene expression, independent of its characterized mitochondrial function in ubiquinone biosynthesis (PubMed:25961505)","subcellular_location":"Mitochondrion inner membrane; Mitochondrion; Nucleus; Chromosome","url":"https://www.uniprot.org/uniprotkb/Q99807/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/COQ7","classification":"Not Classified","n_dependent_lines":237,"n_total_lines":1208,"dependency_fraction":0.19619205298013245},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/COQ7","total_profiled":1310},"omim":[{"mim_id":"620402","title":"NEURONOPATHY, DISTAL HEREDITARY MOTOR, AUTOSOMAL RECESSIVE 9; HMNR9","url":"https://www.omim.org/entry/620402"},{"mim_id":"619956","title":"PIGY UPSTREAM OPEN READING FRAME; 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   \"journal\": \"Science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — functional complementation across species with direct phenotypic rescue, replicated conceptually in multiple subsequent studies\",\n      \"pmids\": [\"9020081\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1996,\n      \"finding\": \"Yeast COQ7 is required for ubiquinone biosynthesis; coq7 mutants lack ubiquinone but accumulate demethoxyubiquinone (DMQ), placing COQ7 at a hydroxylase step converting DMQ to ubiquinone.\",\n      \"method\": \"Genetic deletion and complementation in S. cerevisiae; lipid analysis by HPLC; growth assay on nonfermentable carbon sources\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro biochemical analysis and genetic deletion with rescue, independently replicated across organisms\",\n      \"pmids\": [\"8621692\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"Yeast Coq7p/Cat5p is localized to the mitochondrial inner membrane and is directly involved in ubiquinone biosynthesis; the defect in gluconeogenic gene activation in coq7/cat5 null mutants is a secondary consequence of impaired respiration, not a direct transcriptional function.\",\n      \"method\": \"Subcellular fractionation; mitochondrial localization assay; genetic epistasis with respiration-defective mutants\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — direct localization with functional consequence, epistasis resolving two proposed functions, replicated across labs\",\n      \"pmids\": [\"9452453\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"C. elegans CLK-1 fused to GFP is fully active and localizes to mitochondria in all somatic cells; overexpression of CLK-1 increases mitochondrial activity and accelerates behavioral rates while shortening lifespan, demonstrating a regulatory role in mitochondrial function and aging.\",\n      \"method\": \"GFP fusion protein live imaging; mitochondrial dye-uptake assay in vivo; succinate cytochrome c reductase assay in vitro; transgenic overexpression\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — direct subcellular localization tied to functional consequence, multiple orthogonal methods, overexpression phenotype\",\n      \"pmids\": [\"10202142\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"CLK-1 is absolutely required for ubiquinone (UQ9) biosynthesis in C. elegans; clk-1 mutants lack UQ9 and instead accumulate DMQ9, which can partially substitute as an electron carrier in the respiratory chain.\",\n      \"method\": \"Lipid extraction and HPLC analysis of quinone species; mitochondrial respiratory enzyme activity assays (NADH-cytochrome c reductase, succinate-cytochrome c reductase); chemical synthesis of DMQ2 and functional assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — direct biochemical identification of substrate accumulation and enzymatic bypass, multiple orthogonal methods\",\n      \"pmids\": [\"11244089\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"COQ7 belongs to the di-iron carboxylate oxidase/hydroxylase family based on a conserved iron-ligand sequence motif; bacterial COQ7 homologs from P. aeruginosa and T. ferrooxidans complement an E. coli mutant lacking the 5-demethoxyubiquinone hydroxylase, confirming direct hydroxylase function.\",\n      \"method\": \"Sequence analysis; cloning of bacterial COQ7 homologs; functional complementation of E. coli ubiB mutant; structural modeling\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — functional complementation with structural inference; single lab, no direct iron measurement\",\n      \"pmids\": [\"11435415\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"Mouse COQ7 (mCLK1) is synthesized as a preprotein, imported into the mitochondrial matrix where the leader sequence is cleaved, and becomes loosely associated with the inner membrane; unusually, this import does not require mitochondrial membrane potential.\",\n      \"method\": \"Subcellular fractionation; protease protection assay; import assay with membrane potential uncouplers; immunoblotting of processed vs. precursor forms\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — direct import assay with mutagenesis of targeting sequence and membrane potential manipulation, multiple orthogonal approaches\",\n      \"pmids\": [\"11387338\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"Mouse COQ7 is essential for CoQ9 synthesis; COQ7-deficient mouse embryos fail to synthesize CoQ9 and instead accumulate DMQ9; COQ7 deficiency causes mitochondrial structural abnormalities (enlarged mitochondria with vesicular cristae) and embryonic lethality at E10.5.\",\n      \"method\": \"Targeted gene disruption (knockout mouse); biochemical CoQ analysis; electron microscopy; cell culture rescue experiments\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic knockout with biochemical phenotype (CoQ analysis), structural (EM), and rescue experiments\",\n      \"pmids\": [\"11716496\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"The maternal rescue phenotype of C. elegans clk-1 mutants is explained by persistence of small amounts of maternally provided CLK-1 protein, which is sufficient for synthesis of considerable ubiquinone during early development; gradual depletion of CLK-1 and ubiquinone drives expression of mutant phenotype.\",\n      \"method\": \"Western blotting for CLK-1 protein levels; ubiquinone measurement; developmental arrest experiments; double mutant analysis (daf-2 clk-1)\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — biochemical demonstration of protein persistence linked to UQ levels, single lab\",\n      \"pmids\": [\"14517217\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"C. elegans CLK-1 and mouse CLK-1 have DNA-binding activity specific to the OL (light-strand origin of replication) region of mitochondrial DNA; this activity is inhibited by ADP and is altered by life-span-extending clk-1 mutations.\",\n      \"method\": \"Electrophoretic mobility shift assay (EMSA); competition binding with specific vs. nonspecific DNA; ADP inhibition assay; mutant vs. wild-type protein comparison\",\n      \"journal\": \"FEBS letters\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single lab, single method (EMSA), not independently replicated; functional significance not established\",\n      \"pmids\": [\"11959146\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"C. elegans CLK-1 functions as a demethoxyubiquinone (DMQ) hydroxylase; complementation of E. coli ubiF mutants by C. elegans CLK-1 demonstrated that the eukaryotic CLK-1/Coq7 family can directly catalyze the hydroxylation of DMQ to produce hydroxyubiquinone.\",\n      \"method\": \"Functional complementation of E. coli ubiF mutant; growth on nonfermentable carbon source; ubiquinone synthesis assay\",\n      \"journal\": \"FEBS letters\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — functional complementation across kingdoms demonstrating enzymatic activity, single lab\",\n      \"pmids\": [\"12753928\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"Yeast Coq7p co-migrates with Coq3p and Coq4p as a high-molecular-mass complex; Coq7p (and the quinone lipids DMQ and Q) function to stabilize other Coq polypeptides; E. coli UbiF can substitute for the hydroxylase activity of Coq7p but the structural/stabilization role requires Coq7p itself.\",\n      \"method\": \"Complementation of coq7 point and null mutants by UbiF; gel filtration co-migration analysis; immunoblotting for Coq3, Coq4, Coq6 levels; addition of exogenous Q to null mutant\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple biochemical methods distinguishing enzymatic vs. structural roles, single lab\",\n      \"pmids\": [\"16624818\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"Clioquinol (a metal chelator) inhibits mammalian CLK-1 (COQ7) enzymatic activity in cultured cells; this inhibition is blocked by iron or cobalt cations, indicating chelation of the active-site metal is the mechanism of action.\",\n      \"method\": \"Cell-based CLK-1 activity assay; metal cation rescue experiments (iron, cobalt); phenotypic comparison of clioquinol-treated vs. clk-1 mutant nematodes and mice\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — cell-based enzymatic assay with metal rescue, phenotypic confirmation in two organisms, single lab\",\n      \"pmids\": [\"18927074\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"Mouse CLK-1 (MCLK1) is a di-iron carboxylate protein; Mössbauer and EPR spectroscopy confirmed iron binding; in vitro activity assays showed NADH can serve directly as reductant for the diiron center to activate dioxygen and catalyze substrate oxidation, with no requirement for an additional reductase protein.\",\n      \"method\": \"Heterologous expression in E. coli; Mössbauer spectroscopy; EPR spectroscopy; in vitro enzyme activity assay with quinone substrates and NADH\",\n      \"journal\": \"Biochemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro reconstitution with spectroscopic characterization and substrate assay, multiple orthogonal methods in one study\",\n      \"pmids\": [\"20923139\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"The mitochondrial Ser/Thr phosphatase Ptc7p activates CoQ6 biosynthesis in yeast by dephosphorylating Coq7p; phosphorylated Coq7p is inactive, and Ptc7p-mediated dephosphorylation is required for Coq7p hydroxylase activity.\",\n      \"method\": \"Genetic deletion of PTC7; CoQ6 measurement by HPLC; phosphorylation analysis; epistasis experiments; aerobic growth assays\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic and biochemical evidence for phosphoregulation of Coq7p, single lab with multiple methods\",\n      \"pmids\": [\"23940037\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"COQ9 specifically interacts with COQ7 through conserved residues in mammals; COQ9 has a lipid-binding site and associates with multiple lipid species including CoQ itself; the COQ9 residues necessary for COQ7 interaction form a surface patch around the lipid-binding site, suggesting COQ9 presents its bound lipid substrate to COQ7.\",\n      \"method\": \"Crystal structure of human COQ9 at 2.4 Å; Co-IP/pulldown of COQ9-COQ7 interaction; MS-based lipid identification; disease-associated mouse model with COQ9 mutation showing disrupted CoQ protein complex; mutagenesis of conserved residues\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structure plus biochemical interaction mapping plus mouse disease model, multiple orthogonal methods\",\n      \"pmids\": [\"25339443\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"A nuclear form of CLK-1 exists in C. elegans (and is conserved to humans) that independently regulates lifespan through a retrograde signaling pathway responsive to mitochondrial ROS; nuclear CLK-1 modulates gene expression to regulate mitochondrial ROS metabolism and the mitochondrial unfolded protein response.\",\n      \"method\": \"Subcellular fractionation; fluorescence imaging of tagged CLK-1; genetic epistasis with ROS pathway mutants; gene expression analysis; lifespan assays with nuclear-localized CLK-1 constructs\",\n      \"journal\": \"Nature cell biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct localization experiments plus functional consequence on lifespan and gene expression, single lab; contradicted by PMID 28404998 which did not detect nuclear enrichment\",\n      \"pmids\": [\"25961505\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"The RNA-binding protein HuR stabilizes COQ7 mRNA via binding to the 3'-UTR (first 765 bp); HuR knockdown or serum deprivation destabilizes COQ7 mRNA, reduces COQ7 protein levels, decreases CoQ biosynthesis, reduces oxygen consumption and ATP production, and increases glycolysis.\",\n      \"method\": \"RNA-binding protein pulldown (RIP); mRNA stability assay (half-life measurement); siRNA knockdown of HuR and hnRNP C1/C2; oxygen consumption rate (Seahorse); ATP and lactate measurements\",\n      \"journal\": \"RNA biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct RBP-mRNA interaction assay with functional metabolic readouts, multiple methods, single lab\",\n      \"pmids\": [\"26690054\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"A homozygous COQ7 missense mutation (V141E) in a human patient causes primary CoQ deficiency; 2,4-dihydroxybenzoic acid (2,4-DHB), which bypasses the COQ7 enzymatic step, rescues CoQ levels and biochemical defects in patient fibroblasts.\",\n      \"method\": \"Whole exome sequencing; CoQ measurement by UPLC-MS in patient fibroblasts; rescue with 2,4-DHB; functional mitochondrial assays\",\n      \"journal\": \"Journal of medical genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — biochemical demonstration of enzyme loss with substrate bypass rescue in patient cells, single lab\",\n      \"pmids\": [\"26084283\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"All pleiotropic phenotypes of C. elegans clk-1 null mutants (behavioral, developmental, mitochondrial quality control gene expression, lifespan) are attributable to loss of ubiquinone biosynthesis; pharmacological restoration of UQ biosynthesis rescues all phenotypes; no nuclear enrichment of MCLK1 or CLK-1 was detected in worms or mammalian cell fractionation.\",\n      \"method\": \"Immunohistochemistry in C. elegans; subcellular fractionation in mammalian cells; pharmacological UQ restoration; lifespan analysis; gene expression analysis; CLK-1 constructs lacking mitochondrial targeting sequence\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal methods resolving single-function vs. multi-function debate, single lab; directly contradicts nuclear localization claim\",\n      \"pmids\": [\"28404998\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"COQ7 adopts a ferritin-like (di-iron carboxylate) fold with a hydrophobic channel whose substrate-binding capacity is enhanced by COQ9; two COQ7:COQ9 heterodimers form a curved tetramer that deforms the mitochondrial inner membrane, potentially allowing CoQ intermediates to translocate from the bilayer to the proteins' lipid-binding sites; two tetramers assemble into a soluble octamer with a pseudo-bilayer of lipids captured within.\",\n      \"method\": \"Cryo-EM structure of COQ7:COQ9 complex with bound lipid/substrate/NADH; molecular dynamics simulations; structure-function mutagenesis\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — cryo-EM structure with functional validation and molecular dynamics, multiple orthogonal methods in one study\",\n      \"pmids\": [\"36306796\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Manganese exposure inhibits COQ7 di-iron carboxylate hydroxylase activity in mouse cells; pre-treatment with cobalt interferes with manganese inhibition, suggesting cobalt has greater affinity than both iron and manganese for the COQ7 active site and maintains catalytic activity when substituted.\",\n      \"method\": \"Cell-based COQ7 activity assay (CoQ biosynthesis measurement); manganese and cobalt treatment; competitive metal replacement assay\",\n      \"journal\": \"microPublication biology\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single cell-based assay, single lab, no direct metal occupancy measurement\",\n      \"pmids\": [\"36176269\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"COQ7 (CLK-1) is a mitochondrial di-iron carboxylate hydroxylase that catalyzes the penultimate step of coenzyme Q (ubiquinone) biosynthesis—the hydroxylation of 5-demethoxyubiquinone (DMQ)—using NADH directly as a reductant; it forms a functional complex with the lipid-binding protein COQ9, which presents the hydrophobic CoQ intermediate to COQ7's active site within a membrane-deforming COQ7:COQ9 tetramer, and its hydroxylase activity is post-translationally regulated by dephosphorylation (via Ptc7p in yeast) and by active-site metal occupancy; loss of COQ7 function causes accumulation of DMQ, depletion of CoQ, mitochondrial respiratory failure, and in mammals, embryonic lethality or inherited neurological disease.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"COQ7 (CLK-1) is the mitochondrial di-iron carboxylate hydroxylase that catalyzes a penultimate step of coenzyme Q (ubiquinone) biosynthesis, converting 5-demethoxyubiquinone (DMQ) to the hydroxylated intermediate en route to mature CoQ [#1, #5, #13]. Its requirement for ubiquinone synthesis is deeply conserved: yeast Coq7p, C. elegans CLK-1, and mouse COQ7 are functionally interchangeable, and loss of the enzyme in any of these systems blocks CoQ production and causes accumulation of the DMQ precursor [#0, #1, #4, #7]. The protein is imported into the mitochondrial matrix and associates with the inner membrane, where it operates [#2, #6]. Biochemically, COQ7 carries a ferritin-like di-iron carboxylate center that, with NADH serving directly as the reductant, activates dioxygen for substrate oxidation without a separate reductase, and its activity depends on active-site metal occupancy—chelation by clioquinol abolishes activity in a manner reversed by iron or cobalt [#12, #13]. COQ7 functions in a complex with the lipid-binding protein COQ9: COQ9 presents its bound hydrophobic CoQ intermediate to the COQ7 active site, and two COQ7:COQ9 heterodimers form a curved, membrane-deforming tetramer (assembling further into a lipid-containing octamer) that extracts CoQ intermediates from the bilayer for catalysis [#15, #20]. The enzyme is regulated post-translationally by phosphorylation, with the mitochondrial phosphatase Ptc7p dephosphorylating and thereby activating yeast Coq7p [#14], and at the mRNA level through stabilization of COQ7 transcript by the RNA-binding protein HuR [#17]. Because CoQ is essential for respiration, loss of COQ7 produces mitochondrial respiratory failure, abnormal mitochondrial structure, and embryonic lethality in mouse, and a homozygous COQ7 missense mutation (V141E) causes primary CoQ deficiency disease in humans, rescuable by the bypass metabolite 2,4-dihydroxybenzoic acid [#7, #18]. The pleiotropic developmental, behavioral, and lifespan phenotypes of clk-1 mutants in C. elegans are attributable to loss of ubiquinone biosynthesis [#19].\",\n  \"teleology\": [\n    {\n      \"year\": 1996,\n      \"claim\": \"Established that COQ7 acts at a defined hydroxylase step of ubiquinone biosynthesis by showing its loss blocks CoQ and causes accumulation of the DMQ precursor.\",\n      \"evidence\": \"Genetic deletion/complementation in S. cerevisiae with HPLC lipid analysis and nonfermentable growth assays\",\n      \"pmids\": [\"8621692\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not directly demonstrate enzymatic chemistry or the catalytic cofactor\", \"Substrate-presentation and partner requirements unknown\"]\n    },\n    {\n      \"year\": 1997,\n      \"claim\": \"Demonstrated deep evolutionary conservation of COQ7 function by showing C. elegans clk-1 rescues yeast coq7/cat5 nulls, unifying the gene's role across species.\",\n      \"evidence\": \"Cross-species genetic complementation and sequence homology analysis\",\n      \"pmids\": [\"9020081\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Conservation of function did not define molecular mechanism\", \"Catalytic identity still inferential\"]\n    },\n    {\n      \"year\": 1998,\n      \"claim\": \"Resolved competing functional models by localizing Coq7p to the mitochondrial inner membrane and showing its apparent transcriptional/gluconeogenic role is secondary to respiratory failure.\",\n      \"evidence\": \"Subcellular fractionation and genetic epistasis with respiration-defective mutants\",\n      \"pmids\": [\"9452453\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not establish enzymatic mechanism\", \"Membrane association mode not detailed\"]\n    },\n    {\n      \"year\": 2001,\n      \"claim\": \"Defined COQ7 as a di-iron carboxylate hydroxylase and confirmed its direct enzymatic activity through bacterial homolog complementation, while characterizing its mitochondrial import and the consequences of its loss in metazoans.\",\n      \"evidence\": \"Sequence/structural analysis with E. coli ubiB complementation; import/protease-protection assays; mouse knockout with CoQ analysis and EM; C. elegans quinone HPLC and respiratory assays\",\n      \"pmids\": [\"11435415\", \"11387338\", \"11716496\", \"11244089\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct iron measurement not yet performed\", \"Identity of the in vivo reductant unresolved\", \"How DMQ reaches the active site unknown\"]\n    },\n    {\n      \"year\": 2003,\n      \"claim\": \"Confirmed that the eukaryotic CLK-1/Coq7 family directly catalyzes DMQ hydroxylation, cementing its enzymatic assignment.\",\n      \"evidence\": \"Complementation of E. coli ubiF mutant with growth and ubiquinone synthesis readouts\",\n      \"pmids\": [\"12753928\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single lab; no purified enzyme kinetics\", \"Cofactor chemistry not directly probed\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Separated COQ7's catalytic role from a structural role, showing it (with quinone lipids) stabilizes other Coq polypeptides within a high-molecular-mass biosynthetic complex independent of its hydroxylase chemistry.\",\n      \"evidence\": \"UbiF complementation, gel filtration co-migration, and immunoblotting of Coq3/Coq4/Coq6 in yeast\",\n      \"pmids\": [\"16624818\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Stoichiometry and architecture of the complex undefined\", \"Mechanism of polypeptide stabilization unclear\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Directly proved the di-iron center and showed NADH can serve as the reductant without an accessory reductase, defining the core catalytic mechanism.\",\n      \"evidence\": \"E. coli expression, Mössbauer and EPR spectroscopy, and in vitro activity assays with quinone substrates and NADH\",\n      \"pmids\": [\"20923139\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Physiological reductant in vivo not confirmed\", \"Structural basis of substrate access not yet resolved\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Identified post-translational regulation of COQ7 activity, showing phosphorylated Coq7p is inactive and the phosphatase Ptc7p activates it by dephosphorylation.\",\n      \"evidence\": \"PTC7 deletion, CoQ6 HPLC, phosphorylation analysis, and epistasis/aerobic growth assays in yeast\",\n      \"pmids\": [\"23940037\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Phospho-sites and kinase not fully mapped\", \"Conservation of phosphoregulation in mammals not established here\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Established the molecular basis of COQ7-COQ9 partnership, showing COQ9 binds lipids/CoQ and presents substrate to COQ7 via a defined surface patch.\",\n      \"evidence\": \"Crystal structure of human COQ9, Co-IP/pulldown, MS lipid identification, mutagenesis, and a disease mouse model\",\n      \"pmids\": [\"25339443\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not yet visualize the assembled COQ7:COQ9 complex\", \"Mechanism of lipid handoff inferred not observed\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Extended COQ7 regulation to the transcript level and linked it to human disease, while a contested report proposed a nuclear retrograde-signaling form.\",\n      \"evidence\": \"HuR RIP/mRNA stability with metabolic readouts; patient WES with 2,4-DHB bypass rescue in fibroblasts; subcellular fractionation/lifespan assays for the nuclear-CLK-1 claim\",\n      \"pmids\": [\"26690054\", \"26084283\", \"25961505\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Nuclear localization was not detected in a subsequent study (PMID 28404998)\", \"Generality of HuR regulation across tissues unknown\", \"Single patient for the disease allele\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Argued that all pleiotropic clk-1 phenotypes derive from loss of ubiquinone biosynthesis and found no nuclear enrichment, directly challenging a separate nuclear-signaling function.\",\n      \"evidence\": \"Immunohistochemistry, mammalian fractionation, pharmacological UQ restoration, and lifespan/gene-expression analysis\",\n      \"pmids\": [\"28404998\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single lab; reconciliation with nuclear-CLK-1 report unresolved\", \"Does not exclude minor non-canonical pools\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Provided the structural mechanism of catalysis-in-membrane, showing COQ7:COQ9 heterodimers form a curved tetramer that deforms the inner membrane to extract CoQ intermediates, and refined understanding of active-site metal selectivity.\",\n      \"evidence\": \"Cryo-EM of the COQ7:COQ9 complex with bound lipid/substrate/NADH plus molecular dynamics and mutagenesis; cell-based activity assays with manganese/cobalt metal competition\",\n      \"pmids\": [\"36306796\", \"36176269\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"In vivo relevance of the soluble octamer not established\", \"Metal-occupancy regulation (Mn/Co) rests on single low-confidence cell assay without direct occupancy measurement\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How COQ7 activity is integrated across phosphoregulation, metal occupancy, membrane-deformation dynamics, and tissue-specific regulation to control CoQ output in mammals remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mammalian phosphoregulation circuitry undefined\", \"In vivo physiological reductant and metal-loading control unconfirmed\", \"Spectrum of human COQ7 disease alleles and genotype-phenotype relationships incomplete\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0016491\", \"supporting_discovery_ids\": [1, 5, 10, 13]},\n      {\"term_id\": \"GO:0016787\", \"supporting_discovery_ids\": [1, 5, 10]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005743\", \"supporting_discovery_ids\": [2, 6]},\n      {\"term_id\": \"GO:0005739\", \"supporting_discovery_ids\": [3, 6, 7]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-1430728\", \"supporting_discovery_ids\": [1, 4, 7]}\n    ],\n    \"complexes\": [\"COQ7:COQ9 hydroxylase complex\", \"high-molecular-mass CoQ biosynthetic complex (Coq3/Coq4/Coq7)\"],\n    \"partners\": [\"COQ9\", \"PTC7\", \"ELAVL1 (HuR)\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":8,"faith_total":8,"faith_pct":100.0}}