{"gene":"COQ9","run_date":"2026-06-09T22:57:19","timeline":{"discoveries":[{"year":2005,"finding":"COQ9 (yeast Coq9p) is required for coenzyme Q6 biosynthesis in S. cerevisiae; deletion causes CoQ deficiency and loss of mitochondrial NADH-cytochrome c reductase activity restorable by exogenous CoQ2. COQ8/ABC1 overexpression suppresses the coq9 respiratory defect by increasing mitochondrial concentrations of several CoQ biosynthetic enzymes, suggesting a regulatory or catalytic role for Coq9p in the pathway.","method":"Yeast respiratory-deficient mutant complementation, CoQ measurement, enzyme activity assay, genetic suppression by COQ8/ABC1 overexpression","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods (complementation, biochemical activity, genetic suppression), independently foundational, replicated in subsequent studies","pmids":["16027161"],"is_preprint":false},{"year":2007,"finding":"Yeast Coq9p is a peripheral membrane protein on the matrix side of the mitochondrial inner membrane and is a subunit of a ~1 MDa multi-subunit CoQ biosynthetic complex (CoQ-synthome). Steady-state levels of Coq3, Coq4, Coq6, Coq7, and Coq9 are mutually interdependent. Coq9p physically interacts with Coq4p, Coq5p, Coq6p, and Coq7p as shown by co-immunoprecipitation of HA-tagged Coq9p.","method":"Submitochondrial fractionation, Blue Native-PAGE, co-immunoprecipitation of HA-tagged Coq9p","journal":"Archives of biochemistry and biophysics","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal Co-IP, BN-PAGE, fractionation; replicated across multiple subsequent studies","pmids":["17391640"],"is_preprint":false},{"year":2009,"finding":"A homozygous nonsense mutation in human COQ9 (truncating 75 C-terminal amino acids) causes primary CoQ10 deficiency; patient fibroblasts show CoQ10 biosynthetic rate of 11% of controls and accumulate an abnormal biosynthetic intermediate. The equivalent yeast mutation abolishes respiratory growth, establishing COQ9 as essential for CoQ biosynthesis.","method":"Homozygosity mapping, Sanger sequencing, fibroblast CoQ biosynthesis assay, site-directed mutagenesis of yeast ortholog","journal":"American journal of human genetics","confidence":"High","confidence_rationale":"Tier 2 / Strong — human patient biochemistry confirmed by yeast mutagenesis; multiple orthogonal methods","pmids":["19375058"],"is_preprint":false},{"year":2012,"finding":"In a Coq9 R239X knockin mouse model, loss of functional Coq9 protein causes severe reduction of Coq7 protein levels, widespread CoQ deficiency, and accumulation of demethoxyubiquinone (DMQ). This leads to brain-specific impairment of mitochondrial bioenergetics (reduced respiratory control ratio, ATP levels, ATP/ADP ratio), specific loss of respiratory complex I, neuronal death, and demyelination.","method":"Knockin mouse model (Coq9 R239X), CoQ and DMQ measurement, western blotting for Coq7 protein, mitochondrial respiration assays, histopathology","journal":"Human molecular genetics","confidence":"High","confidence_rationale":"Tier 2 / Strong — in vivo mouse model with multiple biochemical and functional readouts, replicated in subsequent mouse studies","pmids":["23255162"],"is_preprint":false},{"year":2014,"finding":"Human COQ9 is a lipid-binding protein that (1) specifically interacts with COQ7 through conserved surface residues, (2) has structural homology to the TFR family of bacterial transcriptional regulators adopting an atypical dimer orientation, (3) binds multiple lipid species including CoQ itself at a defined lipid-binding site, and (4) a disease-related COQ9 mutation disrupts the entire CoQ biosynthetic complex in a mouse model. The conserved COQ9 residues mediating COQ7 interaction cluster around the lipid-binding site, suggesting COQ9 presents bound lipid to COQ7.","method":"Crystal structure at 2.4 Å (X-ray crystallography), mass spectrometry-based lipid analysis of purified COQ9, mouse model with disease mutation, co-immunoprecipitation/interaction mapping of COQ7-COQ9","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structure plus MS lipid binding plus mouse model, multiple orthogonal methods in one rigorous study","pmids":["25339443"],"is_preprint":false},{"year":2015,"finding":"Yeast Coq9 is required for the deamination of CoQ intermediates derived from para-aminobenzoic acid (pABA): deletion of COQ9 in a coq5-5 background with Coq8 overexpression leads to loss of 13C6-DDMQ6 and persistence of nitrogen-containing intermediates (13C6-4-AP and 13C6-IDDMQ6). Coq9 is also required for the function of Coq6 and Coq7 hydroxylases, and a temperature-sensitive coq9 mutant shows decreased Q6 and increased nitrogen-containing intermediates with concomitant reduction in Coq4, Coq5, Coq6, and Coq7 levels.","method":"Stable isotope labeling (13C6-pABA), LC-MS/MS quantification of CoQ intermediates, temperature-sensitive coq9 mutant, coq9/coq5-5 double mutant analysis, western blotting","journal":"Biochimica et biophysica acta","confidence":"High","confidence_rationale":"Tier 1 / Moderate — stable isotope tracing with MS identification of specific intermediates, multiple genetic backgrounds tested in one study","pmids":["26008578"],"is_preprint":false},{"year":2015,"finding":"Comparison of two Coq9 mouse models (Q95X and R239X) shows that the severity of CoQ deficiency and encephalomyopathy is determined by the stability of the COQ biosynthetic multiprotein complex: the R239X truncation destabilizes the complex causing severe widespread CoQ deficiency and fatal encephalomyopathy, while Q95X produces a truncated protein with milder complex disruption and mild late-onset myopathy. Both models show COQ9 is required for maintaining levels of other COQ biosynthetic proteins.","method":"Knock-in mouse models, CoQ measurement, western blotting of COQ complex subunits, mitochondrial respiration assays, histopathology, treatment with 2,4-diHB","journal":"EMBO molecular medicine","confidence":"High","confidence_rationale":"Tier 2 / Strong — two independent mouse models compared with multiple biochemical and functional readouts, mechanistic link between truncation, complex stability, and disease severity","pmids":["25802402"],"is_preprint":false},{"year":2015,"finding":"Absence of COQ9 protein in human patient fibroblasts (loss-of-function variant) causes concomitant strong reduction of COQ7 protein, significant accumulation of 6-demethoxyubiquinone10 (the COQ7 substrate), severe reduction in total CoQ10, and decreased complex II/III (succinate-cytochrome c oxidoreductase) activity. Lentiviral re-expression of COQ9 restored all parameters, confirming COQ9 is required for COQ7 stability and activity.","method":"Patient fibroblast biochemical analysis (CoQ10 measurement, respiratory chain enzyme assay), western blotting, lentiviral complementation","journal":"European journal of human genetics : EJHG","confidence":"High","confidence_rationale":"Tier 2 / Moderate — lentiviral rescue with multiple biochemical readouts in patient cells, single lab","pmids":["26081641"],"is_preprint":false},{"year":2017,"finding":"Human COQ9 rescues yeast coq9 temperature-sensitive mutants by stabilizing the CoQ-synthome: expression of human COQ9 increases steady-state levels of yeast Coq4, Coq6, Coq7, and Coq9 and enhances CoQ biosynthesis from 4-hydroxybenzoic acid (4HB). Human COQ9 co-purifies with tagged yeast Coq6 (Coq6-CNAP), demonstrating physical interaction with the yeast CoQ biosynthetic complex.","method":"Yeast complementation assay, respiratory growth on non-fermentable carbon source, CoQ6 measurement, western blotting of Coq polypeptides, co-purification with tagged Coq6","journal":"Frontiers in physiology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — complementation plus co-purification, single lab, cross-species system","pmids":["28736527"],"is_preprint":false},{"year":2022,"finding":"Cryo-EM/structural analysis reveals that COQ7 adopts a ferritin-like 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 membrane, potentially opening a pathway for CoQ intermediates to translocate from the bilayer to the proteins' lipid-binding sites. Two such tetramers assemble into a soluble octamer with a pseudo-bilayer of lipids captured within. Molecular dynamics simulations support membrane deformation. The complex is captured in lipid-, substrate-, and NADH-bound states.","method":"Cryo-EM structure determination, molecular dynamics simulations, reconstitution of COQ7:COQ9 complex, lipid/substrate/NADH binding assays","journal":"Molecular cell","confidence":"High","confidence_rationale":"Tier 1 / Strong — cryo-EM structure with substrate/cofactor-bound states plus molecular dynamics plus reconstitution in a single rigorous study","pmids":["36306796"],"is_preprint":false}],"current_model":"COQ9 is a lipid-binding, TFR-fold protein that is an essential structural and functional subunit of the mitochondrial CoQ biosynthetic complex (CoQ-synthome): it physically interacts with COQ7 (and other COQ proteins) to stabilize the multiprotein complex, enhances COQ7's substrate-binding capacity through a hydrophobic channel, forms a curved COQ7:COQ9 tetramer that deforms the inner mitochondrial membrane to facilitate CoQ intermediate access, and is required for the deamination of pABA-derived CoQ intermediates and the hydroxylase activities of COQ6 and COQ7 — with loss of COQ9 causing COQ7 destabilization, DMQ accumulation, severe CoQ deficiency, and mitochondrial respiratory chain dysfunction."},"narrative":{"mechanistic_narrative":"COQ9 is an essential, lipid-binding subunit of the mitochondrial CoQ biosynthetic complex (the CoQ-synthome), required for coenzyme Q biosynthesis from yeast to human [PMID:16027161, PMID:19375058]. It associates with the matrix face of the inner membrane as part of a ~1 MDa multi-subunit complex, physically interacting with COQ4, COQ5, COQ6, and COQ7 and maintaining the mutual steady-state stability of these subunits [PMID:17391640]. Its central biochemical role is to stabilize and activate COQ7: COQ9 binds COQ7 through conserved surface residues clustered around its lipid-binding site, and structural work shows COQ9 enhances the substrate-binding capacity of COQ7's hydrophobic channel, with two COQ7:COQ9 heterodimers forming a curved tetramer that deforms the membrane to route lipophilic CoQ intermediates from the bilayer to the enzymes' active sites [PMID:25339443, PMID:36306796]. COQ9 is also required for the deamination of pABA-derived CoQ intermediates and for the hydroxylase activities of COQ6 and COQ7 [PMID:26008578]. Loss of COQ9 destabilizes COQ7, causes accumulation of the COQ7 substrate demethoxyubiquinone (DMQ), and produces severe CoQ deficiency with respiratory-chain dysfunction [PMID:23255162, PMID:26081641]. In humans, truncating COQ9 mutations cause primary CoQ10 deficiency, and the severity of the resulting encephalomyopathy tracks with the degree of CoQ-synthome destabilization [PMID:19375058, PMID:25802402].","teleology":[{"year":2005,"claim":"Established that COQ9 is a required component of the CoQ biosynthetic pathway rather than an incidental factor, by showing its deletion abolishes CoQ synthesis and respiration.","evidence":"Yeast coq9 mutant complementation, CoQ and enzyme activity assays, genetic suppression by COQ8/ABC1 overexpression","pmids":["16027161"],"confidence":"High","gaps":["Did not define whether COQ9 is catalytic, structural, or regulatory","No physical partners identified"]},{"year":2007,"claim":"Placed COQ9 physically within a ~1 MDa membrane-associated multi-subunit complex and identified its direct neighbors, reframing it as a structural hub whose loss destabilizes other COQ proteins.","evidence":"Submitochondrial fractionation, Blue Native-PAGE, and reciprocal co-immunoprecipitation of HA-tagged yeast Coq9p","pmids":["17391640"],"confidence":"High","gaps":["Did not resolve which interaction is direct versus complex-mediated","No mechanistic role in catalysis defined"]},{"year":2009,"claim":"Demonstrated COQ9 relevance to human disease by linking a truncating mutation to primary CoQ10 deficiency, with cross-species validation in yeast.","evidence":"Homozygosity mapping, patient fibroblast CoQ biosynthesis assay, and site-directed mutagenesis of the yeast ortholog","pmids":["19375058"],"confidence":"High","gaps":["Identity of the accumulating intermediate not defined","Molecular function of the C-terminus left open"]},{"year":2012,"claim":"Linked COQ9 loss to a specific downstream lesion — COQ7 destabilization and DMQ accumulation — and to tissue-specific bioenergetic failure in vivo.","evidence":"Coq9 R239X knock-in mouse model with CoQ/DMQ measurement, COQ7 western blotting, respiration assays, and histopathology","pmids":["23255162"],"confidence":"High","gaps":["Did not explain the molecular basis of COQ7 dependence on COQ9","Brain-specific vulnerability mechanism unresolved"]},{"year":2014,"claim":"Provided the structural and biochemical mechanism: COQ9 is a lipid-binding TFR-fold protein that binds COQ7 via residues around its lipid-binding pocket, suggesting it presents lipid substrate to COQ7.","evidence":"2.4 Å crystal structure, MS-based lipid analysis of purified COQ9, interaction mapping, and a disease-mutation mouse model","pmids":["25339443"],"confidence":"High","gaps":["Did not show the assembled COQ7:COQ9 complex architecture","Mode of substrate hand-off to COQ7 inferred, not visualized"]},{"year":2015,"claim":"Defined COQ9's catalytic-support role in the pathway: it is required for deamination of pABA-derived intermediates and for COQ6/COQ7 hydroxylase function.","evidence":"13C6-pABA stable isotope labeling, LC-MS/MS of CoQ intermediates, and temperature-sensitive/double-mutant yeast analysis","pmids":["26008578"],"confidence":"High","gaps":["The deaminase enzyme itself not identified","COQ9's direct versus indirect role in deamination not separated"]},{"year":2015,"claim":"Showed that disease severity is set by the degree to which the COQ9 truncation destabilizes the biosynthetic complex, connecting genotype to complex stability to phenotype.","evidence":"Comparison of Q95X and R239X knock-in mouse models with CoQ measurement, COQ subunit western blotting, respiration, and 2,4-diHB treatment","pmids":["25802402"],"confidence":"High","gaps":["Did not define structural basis of differential complex destabilization","Therapeutic response durability not addressed"]},{"year":2015,"claim":"Confirmed in human patient cells that COQ9 loss specifically collapses COQ7 protein and activity, with full rescue on re-expression establishing direct dependence.","evidence":"Patient fibroblast CoQ10 and respiratory enzyme assays, western blotting, and lentiviral COQ9 complementation","pmids":["26081641"],"confidence":"High","gaps":["Single-lab study","Whether other COQ subunits are similarly dependent not fully resolved here"]},{"year":2017,"claim":"Demonstrated functional conservation by showing human COQ9 stabilizes the yeast CoQ-synthome and physically joins the yeast complex.","evidence":"Yeast complementation, CoQ6 measurement, COQ subunit western blotting, and co-purification with tagged yeast Coq6","pmids":["28736527"],"confidence":"Medium","gaps":["Cross-species system may not fully recapitulate human complex","Directness of human COQ9–yeast Coq6 contact not mapped"]},{"year":2022,"claim":"Resolved the assembled mechanism: COQ7:COQ9 heterodimers form a curved tetramer that deforms the membrane, opening a route for lipophilic intermediates from the bilayer to the enzymes' active sites.","evidence":"Cryo-EM of COQ7:COQ9 in lipid-, substrate-, and NADH-bound states, molecular dynamics simulations, and in vitro reconstitution","pmids":["36306796"],"confidence":"High","gaps":["Higher-order integration into the full ~1 MDa synthome not resolved","In vivo relevance of the soluble octamer not established"]},{"year":null,"claim":"How the COQ7:COQ9 module integrates into the full multi-subunit CoQ-synthome and how lipid intermediates are channeled between successive enzymes remains unresolved.","evidence":"","pmids":[],"confidence":"High","gaps":["No structure of the complete synthome","Mechanism of intermediate transfer between COQ enzymes unknown","Identity of the pABA deaminase activity unresolved"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0008289","term_label":"lipid binding","supporting_discovery_ids":[4,9]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[4,5,7,9]}],"localization":[{"term_id":"GO:0005739","term_label":"mitochondrion","supporting_discovery_ids":[1,3]}],"pathway":[{"term_id":"R-HSA-1430728","term_label":"Metabolism","supporting_discovery_ids":[0,2,5]}],"complexes":["CoQ-synthome (CoQ biosynthetic complex)","COQ7:COQ9 tetramer"],"partners":["COQ7","COQ4","COQ5","COQ6"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"O75208","full_name":"Ubiquinone biosynthesis protein COQ9, mitochondrial","aliases":[],"length_aa":318,"mass_kda":35.5,"function":"Membrane-associated protein that warps the membrane surface to access and bind aromatic isoprenes with high specificity, including ubiquinone (CoQ) isoprene intermediates and presents them directly to COQ7, therefore facilitating the COQ7-mediated hydroxylase step (PubMed:25339443, PubMed:30661980, PubMed:38425362). Participates in the biosynthesis of coenzyme Q, also named ubiquinone, an essential lipid-soluble electron transporter for aerobic cellular respiration (PubMed:25339443, PubMed:30661980)","subcellular_location":"Mitochondrion","url":"https://www.uniprot.org/uniprotkb/O75208/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/COQ9","classification":"Not Classified","n_dependent_lines":14,"n_total_lines":1208,"dependency_fraction":0.011589403973509934},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/COQ9","total_profiled":1310},"omim":[{"mim_id":"621162","title":"AARF DOMAIN-CONTAINING KINASE 2; ADCK2","url":"https://www.omim.org/entry/621162"},{"mim_id":"615030","title":"SPASTIC PARAPLEGIA 56, AUTOSOMAL RECESSIVE, WITH OR WITHOUT PSEUDOXANTHOMA ELASTICUM; SPG56","url":"https://www.omim.org/entry/615030"},{"mim_id":"614654","title":"COENZYME Q10 DEFICIENCY, PRIMARY, 5; COQ10D5","url":"https://www.omim.org/entry/614654"},{"mim_id":"614647","title":"COENZYME Q6, MONOOXYGENASE; COQ6","url":"https://www.omim.org/entry/614647"},{"mim_id":"612837","title":"COENZYME 9; COQ9","url":"https://www.omim.org/entry/612837"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Mitochondria","reliability":"Approved"},{"location":"Cytosol","reliability":"Approved"}],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in all","driving_tissues":[{"tissue":"skeletal muscle","ntpm":239.3},{"tissue":"tongue","ntpm":225.2}],"url":"https://www.proteinatlas.org/search/COQ9"},"hgnc":{"alias_symbol":["DKFZP434K046"],"prev_symbol":["C16orf49"]},"alphafold":{"accession":"O75208","domains":[{"cath_id":"-","chopping":"96-141","consensus_level":"medium","plddt":97.1561,"start":96,"end":141},{"cath_id":"1.10.357","chopping":"147-296","consensus_level":"high","plddt":93.3813,"start":147,"end":296}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/O75208","model_url":"https://alphafold.ebi.ac.uk/files/AF-O75208-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-O75208-F1-predicted_aligned_error_v6.png","plddt_mean":77.62},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=COQ9","jax_strain_url":"https://www.jax.org/strain/search?query=COQ9"},"sequence":{"accession":"O75208","fasta_url":"https://rest.uniprot.org/uniprotkb/O75208.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/O75208/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/O75208"}},"corpus_meta":[{"pmid":"19375058","id":"PMC_19375058","title":"A nonsense mutation in COQ9 causes autosomal-recessive neonatal-onset primary coenzyme Q10 deficiency: a potentially treatable form of mitochondrial disease.","date":"2009","source":"American journal of human genetics","url":"https://pubmed.ncbi.nlm.nih.gov/19375058","citation_count":182,"is_preprint":false},{"pmid":"25339443","id":"PMC_25339443","title":"Mitochondrial COQ9 is a lipid-binding protein that associates with COQ7 to enable coenzyme Q biosynthesis.","date":"2014","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/25339443","citation_count":104,"is_preprint":false},{"pmid":"23255162","id":"PMC_23255162","title":"Dysfunctional Coq9 protein causes predominant encephalomyopathy associated with CoQ deficiency.","date":"2012","source":"Human molecular genetics","url":"https://pubmed.ncbi.nlm.nih.gov/23255162","citation_count":90,"is_preprint":false},{"pmid":"16027161","id":"PMC_16027161","title":"COQ9, a new gene required for the biosynthesis of coenzyme Q in Saccharomyces cerevisiae.","date":"2005","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/16027161","citation_count":82,"is_preprint":false},{"pmid":"17391640","id":"PMC_17391640","title":"Saccharomyces cerevisiae Coq9 polypeptide is a subunit of the mitochondrial coenzyme Q biosynthetic complex.","date":"2007","source":"Archives of biochemistry and biophysics","url":"https://pubmed.ncbi.nlm.nih.gov/17391640","citation_count":81,"is_preprint":false},{"pmid":"25802402","id":"PMC_25802402","title":"The clinical heterogeneity of coenzyme Q10 deficiency results from genotypic differences in the Coq9 gene.","date":"2015","source":"EMBO molecular medicine","url":"https://pubmed.ncbi.nlm.nih.gov/25802402","citation_count":77,"is_preprint":false},{"pmid":"26081641","id":"PMC_26081641","title":"Fatal neonatal encephalopathy and lactic acidosis caused by a homozygous loss-of-function variant in COQ9.","date":"2015","source":"European journal of human genetics : EJHG","url":"https://pubmed.ncbi.nlm.nih.gov/26081641","citation_count":43,"is_preprint":false},{"pmid":"30482867","id":"PMC_30482867","title":"β-RA reduces DMQ/CoQ ratio and rescues the encephalopathic phenotype in Coq9 mice.","date":"2019","source":"EMBO molecular medicine","url":"https://pubmed.ncbi.nlm.nih.gov/30482867","citation_count":39,"is_preprint":false},{"pmid":"28339599","id":"PMC_28339599","title":"A single nucleotide polymorphism in COQ9 affects mitochondrial and ovarian function and fertility in Holstein cows.","date":"2017","source":"Biology of reproduction","url":"https://pubmed.ncbi.nlm.nih.gov/28339599","citation_count":36,"is_preprint":false},{"pmid":"29560582","id":"PMC_29560582","title":"A family segregating lethal neonatal coenzyme Q10 deficiency caused by mutations in COQ9.","date":"2018","source":"Journal of inherited metabolic disease","url":"https://pubmed.ncbi.nlm.nih.gov/29560582","citation_count":35,"is_preprint":false},{"pmid":"36306796","id":"PMC_36306796","title":"Structure and functionality of a multimeric human COQ7:COQ9 complex.","date":"2022","source":"Molecular cell","url":"https://pubmed.ncbi.nlm.nih.gov/36306796","citation_count":34,"is_preprint":false},{"pmid":"26008578","id":"PMC_26008578","title":"Yeast Coq9 controls deamination of coenzyme Q intermediates that derive from para-aminobenzoic acid.","date":"2015","source":"Biochimica et biophysica acta","url":"https://pubmed.ncbi.nlm.nih.gov/26008578","citation_count":26,"is_preprint":false},{"pmid":"31821167","id":"PMC_31821167","title":"A rare case of primary coenzyme Q10 deficiency due to COQ9 mutation.","date":"2020","source":"Journal of pediatric endocrinology & metabolism : JPEM","url":"https://pubmed.ncbi.nlm.nih.gov/31821167","citation_count":19,"is_preprint":false},{"pmid":"28736527","id":"PMC_28736527","title":"Human COQ9 Rescues a coq9 Yeast Mutant by Enhancing Coenzyme Q Biosynthesis from 4-Hydroxybenzoic Acid and Stabilizing the CoQ-Synthome.","date":"2017","source":"Frontiers in physiology","url":"https://pubmed.ncbi.nlm.nih.gov/28736527","citation_count":11,"is_preprint":false},{"pmid":"40579432","id":"PMC_40579432","title":"Homozygous COQ9 mutation: a new cause of potentially treatable hereditary spastic paraplegia.","date":"2025","source":"European journal of human genetics : EJHG","url":"https://pubmed.ncbi.nlm.nih.gov/40579432","citation_count":3,"is_preprint":false},{"pmid":"33029215","id":"PMC_33029215","title":"Effect of COQ9 and STAT5A polymorphisms on reproductive performance in a Holstein cow herd in Mexico.","date":"2020","source":"Animal reproduction","url":"https://pubmed.ncbi.nlm.nih.gov/33029215","citation_count":1,"is_preprint":false},{"pmid":"40062559","id":"PMC_40062559","title":"Two cases of neonatal hyperglycemia caused by a homozygous COQ9 stop-gain variant.","date":"2025","source":"Journal of diabetes investigation","url":"https://pubmed.ncbi.nlm.nih.gov/40062559","citation_count":1,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":10399,"output_tokens":3062,"usd":0.038564,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":10543,"output_tokens":3248,"usd":0.066958,"stage2_stop_reason":"end_turn"},"total_usd":0.105522,"stage1_batch_id":"msgbatch_01ACAxJQabDsht39JXeWG22d","stage2_batch_id":"msgbatch_01QEU22A9U5sbPTgsMzTmvSf","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2005,\n      \"finding\": \"COQ9 (yeast Coq9p) is required for coenzyme Q6 biosynthesis in S. cerevisiae; deletion causes CoQ deficiency and loss of mitochondrial NADH-cytochrome c reductase activity restorable by exogenous CoQ2. COQ8/ABC1 overexpression suppresses the coq9 respiratory defect by increasing mitochondrial concentrations of several CoQ biosynthetic enzymes, suggesting a regulatory or catalytic role for Coq9p in the pathway.\",\n      \"method\": \"Yeast respiratory-deficient mutant complementation, CoQ measurement, enzyme activity assay, genetic suppression by COQ8/ABC1 overexpression\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods (complementation, biochemical activity, genetic suppression), independently foundational, replicated in subsequent studies\",\n      \"pmids\": [\"16027161\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"Yeast Coq9p is a peripheral membrane protein on the matrix side of the mitochondrial inner membrane and is a subunit of a ~1 MDa multi-subunit CoQ biosynthetic complex (CoQ-synthome). Steady-state levels of Coq3, Coq4, Coq6, Coq7, and Coq9 are mutually interdependent. Coq9p physically interacts with Coq4p, Coq5p, Coq6p, and Coq7p as shown by co-immunoprecipitation of HA-tagged Coq9p.\",\n      \"method\": \"Submitochondrial fractionation, Blue Native-PAGE, co-immunoprecipitation of HA-tagged Coq9p\",\n      \"journal\": \"Archives of biochemistry and biophysics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal Co-IP, BN-PAGE, fractionation; replicated across multiple subsequent studies\",\n      \"pmids\": [\"17391640\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"A homozygous nonsense mutation in human COQ9 (truncating 75 C-terminal amino acids) causes primary CoQ10 deficiency; patient fibroblasts show CoQ10 biosynthetic rate of 11% of controls and accumulate an abnormal biosynthetic intermediate. The equivalent yeast mutation abolishes respiratory growth, establishing COQ9 as essential for CoQ biosynthesis.\",\n      \"method\": \"Homozygosity mapping, Sanger sequencing, fibroblast CoQ biosynthesis assay, site-directed mutagenesis of yeast ortholog\",\n      \"journal\": \"American journal of human genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — human patient biochemistry confirmed by yeast mutagenesis; multiple orthogonal methods\",\n      \"pmids\": [\"19375058\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"In a Coq9 R239X knockin mouse model, loss of functional Coq9 protein causes severe reduction of Coq7 protein levels, widespread CoQ deficiency, and accumulation of demethoxyubiquinone (DMQ). This leads to brain-specific impairment of mitochondrial bioenergetics (reduced respiratory control ratio, ATP levels, ATP/ADP ratio), specific loss of respiratory complex I, neuronal death, and demyelination.\",\n      \"method\": \"Knockin mouse model (Coq9 R239X), CoQ and DMQ measurement, western blotting for Coq7 protein, mitochondrial respiration assays, histopathology\",\n      \"journal\": \"Human molecular genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — in vivo mouse model with multiple biochemical and functional readouts, replicated in subsequent mouse studies\",\n      \"pmids\": [\"23255162\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Human COQ9 is a lipid-binding protein that (1) specifically interacts with COQ7 through conserved surface residues, (2) has structural homology to the TFR family of bacterial transcriptional regulators adopting an atypical dimer orientation, (3) binds multiple lipid species including CoQ itself at a defined lipid-binding site, and (4) a disease-related COQ9 mutation disrupts the entire CoQ biosynthetic complex in a mouse model. The conserved COQ9 residues mediating COQ7 interaction cluster around the lipid-binding site, suggesting COQ9 presents bound lipid to COQ7.\",\n      \"method\": \"Crystal structure at 2.4 Å (X-ray crystallography), mass spectrometry-based lipid analysis of purified COQ9, mouse model with disease mutation, co-immunoprecipitation/interaction mapping of COQ7-COQ9\",\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 MS lipid binding plus mouse model, multiple orthogonal methods in one rigorous study\",\n      \"pmids\": [\"25339443\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Yeast Coq9 is required for the deamination of CoQ intermediates derived from para-aminobenzoic acid (pABA): deletion of COQ9 in a coq5-5 background with Coq8 overexpression leads to loss of 13C6-DDMQ6 and persistence of nitrogen-containing intermediates (13C6-4-AP and 13C6-IDDMQ6). Coq9 is also required for the function of Coq6 and Coq7 hydroxylases, and a temperature-sensitive coq9 mutant shows decreased Q6 and increased nitrogen-containing intermediates with concomitant reduction in Coq4, Coq5, Coq6, and Coq7 levels.\",\n      \"method\": \"Stable isotope labeling (13C6-pABA), LC-MS/MS quantification of CoQ intermediates, temperature-sensitive coq9 mutant, coq9/coq5-5 double mutant analysis, western blotting\",\n      \"journal\": \"Biochimica et biophysica acta\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — stable isotope tracing with MS identification of specific intermediates, multiple genetic backgrounds tested in one study\",\n      \"pmids\": [\"26008578\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Comparison of two Coq9 mouse models (Q95X and R239X) shows that the severity of CoQ deficiency and encephalomyopathy is determined by the stability of the COQ biosynthetic multiprotein complex: the R239X truncation destabilizes the complex causing severe widespread CoQ deficiency and fatal encephalomyopathy, while Q95X produces a truncated protein with milder complex disruption and mild late-onset myopathy. Both models show COQ9 is required for maintaining levels of other COQ biosynthetic proteins.\",\n      \"method\": \"Knock-in mouse models, CoQ measurement, western blotting of COQ complex subunits, mitochondrial respiration assays, histopathology, treatment with 2,4-diHB\",\n      \"journal\": \"EMBO molecular medicine\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — two independent mouse models compared with multiple biochemical and functional readouts, mechanistic link between truncation, complex stability, and disease severity\",\n      \"pmids\": [\"25802402\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Absence of COQ9 protein in human patient fibroblasts (loss-of-function variant) causes concomitant strong reduction of COQ7 protein, significant accumulation of 6-demethoxyubiquinone10 (the COQ7 substrate), severe reduction in total CoQ10, and decreased complex II/III (succinate-cytochrome c oxidoreductase) activity. Lentiviral re-expression of COQ9 restored all parameters, confirming COQ9 is required for COQ7 stability and activity.\",\n      \"method\": \"Patient fibroblast biochemical analysis (CoQ10 measurement, respiratory chain enzyme assay), western blotting, lentiviral complementation\",\n      \"journal\": \"European journal of human genetics : EJHG\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — lentiviral rescue with multiple biochemical readouts in patient cells, single lab\",\n      \"pmids\": [\"26081641\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Human COQ9 rescues yeast coq9 temperature-sensitive mutants by stabilizing the CoQ-synthome: expression of human COQ9 increases steady-state levels of yeast Coq4, Coq6, Coq7, and Coq9 and enhances CoQ biosynthesis from 4-hydroxybenzoic acid (4HB). Human COQ9 co-purifies with tagged yeast Coq6 (Coq6-CNAP), demonstrating physical interaction with the yeast CoQ biosynthetic complex.\",\n      \"method\": \"Yeast complementation assay, respiratory growth on non-fermentable carbon source, CoQ6 measurement, western blotting of Coq polypeptides, co-purification with tagged Coq6\",\n      \"journal\": \"Frontiers in physiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — complementation plus co-purification, single lab, cross-species system\",\n      \"pmids\": [\"28736527\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Cryo-EM/structural analysis reveals that COQ7 adopts a ferritin-like 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 membrane, potentially opening a pathway for CoQ intermediates to translocate from the bilayer to the proteins' lipid-binding sites. Two such tetramers assemble into a soluble octamer with a pseudo-bilayer of lipids captured within. Molecular dynamics simulations support membrane deformation. The complex is captured in lipid-, substrate-, and NADH-bound states.\",\n      \"method\": \"Cryo-EM structure determination, molecular dynamics simulations, reconstitution of COQ7:COQ9 complex, lipid/substrate/NADH binding assays\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — cryo-EM structure with substrate/cofactor-bound states plus molecular dynamics plus reconstitution in a single rigorous study\",\n      \"pmids\": [\"36306796\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"COQ9 is a lipid-binding, TFR-fold protein that is an essential structural and functional subunit of the mitochondrial CoQ biosynthetic complex (CoQ-synthome): it physically interacts with COQ7 (and other COQ proteins) to stabilize the multiprotein complex, enhances COQ7's substrate-binding capacity through a hydrophobic channel, forms a curved COQ7:COQ9 tetramer that deforms the inner mitochondrial membrane to facilitate CoQ intermediate access, and is required for the deamination of pABA-derived CoQ intermediates and the hydroxylase activities of COQ6 and COQ7 — with loss of COQ9 causing COQ7 destabilization, DMQ accumulation, severe CoQ deficiency, and mitochondrial respiratory chain dysfunction.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"COQ9 is an essential, lipid-binding subunit of the mitochondrial CoQ biosynthetic complex (the CoQ-synthome), required for coenzyme Q biosynthesis from yeast to human [#0, #2]. It associates with the matrix face of the inner membrane as part of a ~1 MDa multi-subunit complex, physically interacting with COQ4, COQ5, COQ6, and COQ7 and maintaining the mutual steady-state stability of these subunits [#1]. Its central biochemical role is to stabilize and activate COQ7: COQ9 binds COQ7 through conserved surface residues clustered around its lipid-binding site, and structural work shows COQ9 enhances the substrate-binding capacity of COQ7's hydrophobic channel, with two COQ7:COQ9 heterodimers forming a curved tetramer that deforms the membrane to route lipophilic CoQ intermediates from the bilayer to the enzymes' active sites [#4, #9]. COQ9 is also required for the deamination of pABA-derived CoQ intermediates and for the hydroxylase activities of COQ6 and COQ7 [#5]. Loss of COQ9 destabilizes COQ7, causes accumulation of the COQ7 substrate demethoxyubiquinone (DMQ), and produces severe CoQ deficiency with respiratory-chain dysfunction [#3, #7]. In humans, truncating COQ9 mutations cause primary CoQ10 deficiency, and the severity of the resulting encephalomyopathy tracks with the degree of CoQ-synthome destabilization [#2, #6].\",\n  \"teleology\": [\n    {\n      \"year\": 2005,\n      \"claim\": \"Established that COQ9 is a required component of the CoQ biosynthetic pathway rather than an incidental factor, by showing its deletion abolishes CoQ synthesis and respiration.\",\n      \"evidence\": \"Yeast coq9 mutant complementation, CoQ and enzyme activity assays, genetic suppression by COQ8/ABC1 overexpression\",\n      \"pmids\": [\"16027161\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not define whether COQ9 is catalytic, structural, or regulatory\", \"No physical partners identified\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Placed COQ9 physically within a ~1 MDa membrane-associated multi-subunit complex and identified its direct neighbors, reframing it as a structural hub whose loss destabilizes other COQ proteins.\",\n      \"evidence\": \"Submitochondrial fractionation, Blue Native-PAGE, and reciprocal co-immunoprecipitation of HA-tagged yeast Coq9p\",\n      \"pmids\": [\"17391640\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not resolve which interaction is direct versus complex-mediated\", \"No mechanistic role in catalysis defined\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Demonstrated COQ9 relevance to human disease by linking a truncating mutation to primary CoQ10 deficiency, with cross-species validation in yeast.\",\n      \"evidence\": \"Homozygosity mapping, patient fibroblast CoQ biosynthesis assay, and site-directed mutagenesis of the yeast ortholog\",\n      \"pmids\": [\"19375058\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Identity of the accumulating intermediate not defined\", \"Molecular function of the C-terminus left open\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Linked COQ9 loss to a specific downstream lesion — COQ7 destabilization and DMQ accumulation — and to tissue-specific bioenergetic failure in vivo.\",\n      \"evidence\": \"Coq9 R239X knock-in mouse model with CoQ/DMQ measurement, COQ7 western blotting, respiration assays, and histopathology\",\n      \"pmids\": [\"23255162\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not explain the molecular basis of COQ7 dependence on COQ9\", \"Brain-specific vulnerability mechanism unresolved\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Provided the structural and biochemical mechanism: COQ9 is a lipid-binding TFR-fold protein that binds COQ7 via residues around its lipid-binding pocket, suggesting it presents lipid substrate to COQ7.\",\n      \"evidence\": \"2.4 Å crystal structure, MS-based lipid analysis of purified COQ9, interaction mapping, and a disease-mutation mouse model\",\n      \"pmids\": [\"25339443\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not show the assembled COQ7:COQ9 complex architecture\", \"Mode of substrate hand-off to COQ7 inferred, not visualized\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Defined COQ9's catalytic-support role in the pathway: it is required for deamination of pABA-derived intermediates and for COQ6/COQ7 hydroxylase function.\",\n      \"evidence\": \"13C6-pABA stable isotope labeling, LC-MS/MS of CoQ intermediates, and temperature-sensitive/double-mutant yeast analysis\",\n      \"pmids\": [\"26008578\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"The deaminase enzyme itself not identified\", \"COQ9's direct versus indirect role in deamination not separated\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Showed that disease severity is set by the degree to which the COQ9 truncation destabilizes the biosynthetic complex, connecting genotype to complex stability to phenotype.\",\n      \"evidence\": \"Comparison of Q95X and R239X knock-in mouse models with CoQ measurement, COQ subunit western blotting, respiration, and 2,4-diHB treatment\",\n      \"pmids\": [\"25802402\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not define structural basis of differential complex destabilization\", \"Therapeutic response durability not addressed\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Confirmed in human patient cells that COQ9 loss specifically collapses COQ7 protein and activity, with full rescue on re-expression establishing direct dependence.\",\n      \"evidence\": \"Patient fibroblast CoQ10 and respiratory enzyme assays, western blotting, and lentiviral COQ9 complementation\",\n      \"pmids\": [\"26081641\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Single-lab study\", \"Whether other COQ subunits are similarly dependent not fully resolved here\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Demonstrated functional conservation by showing human COQ9 stabilizes the yeast CoQ-synthome and physically joins the yeast complex.\",\n      \"evidence\": \"Yeast complementation, CoQ6 measurement, COQ subunit western blotting, and co-purification with tagged yeast Coq6\",\n      \"pmids\": [\"28736527\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Cross-species system may not fully recapitulate human complex\", \"Directness of human COQ9–yeast Coq6 contact not mapped\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Resolved the assembled mechanism: COQ7:COQ9 heterodimers form a curved tetramer that deforms the membrane, opening a route for lipophilic intermediates from the bilayer to the enzymes' active sites.\",\n      \"evidence\": \"Cryo-EM of COQ7:COQ9 in lipid-, substrate-, and NADH-bound states, molecular dynamics simulations, and in vitro reconstitution\",\n      \"pmids\": [\"36306796\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Higher-order integration into the full ~1 MDa synthome not resolved\", \"In vivo relevance of the soluble octamer not established\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How the COQ7:COQ9 module integrates into the full multi-subunit CoQ-synthome and how lipid intermediates are channeled between successive enzymes remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No structure of the complete synthome\", \"Mechanism of intermediate transfer between COQ enzymes unknown\", \"Identity of the pABA deaminase activity unresolved\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0008289\", \"supporting_discovery_ids\": [4, 9]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [4, 5, 7, 9]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005739\", \"supporting_discovery_ids\": [1, 3]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-1430728\", \"supporting_discovery_ids\": [0, 2, 5]}\n    ],\n    \"complexes\": [\"CoQ-synthome (CoQ biosynthetic complex)\", \"COQ7:COQ9 tetramer\"],\n    \"partners\": [\"COQ7\", \"COQ4\", \"COQ5\", \"COQ6\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":6,"faith_total":6,"faith_pct":100.0}}