{"gene":"MOCS2","run_date":"2026-06-10T02:59:50","timeline":{"discoveries":[{"year":2003,"finding":"MOCS2 has a bicistronic architecture encoding two proteins (MOCS2A and MOCS2B) in different, overlapping open reading frames. These proteins are expressed either from different mRNAs generated by alternative splicing or by independent translation of a bicistronic mRNA, forming the small and large subunits of molybdopterin synthase respectively.","method":"Molecular cloning, alternative splicing analysis, bicistronic mRNA characterization","journal":"Human mutation","confidence":"High","confidence_rationale":"Tier 2 / Strong — independently replicated across multiple labs and papers, confirmed by experimental expression studies and functional characterization","pmids":["12754701","16737835"],"is_preprint":false},{"year":2005,"finding":"A MOCS2B mutation that eliminates the stop codon (elongating the large subunit) abolishes the binding affinity of MOCS2B for both precursor Z (the substrate) and the small subunit MOCS2A, demonstrating that the C-terminus of MOCS2B is required for substrate binding and subunit interaction.","method":"In vitro expression of mutant protein, binding assay for precursor Z and MOCS2A interaction","journal":"Human genetics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct in vitro binding assay with mutagenesis, single lab","pmids":["16021469"],"is_preprint":false},{"year":2006,"finding":"MOCS2B (large subunit of molybdopterin synthase) is unstable in the absence of MOCS2A (small subunit), revealing that the two subunits are co-dependent for protein stability; both transcripts are produced normally from a deletion removing the MOCS2A start codon, but MOCS2B protein is degraded without its partner.","method":"Western blot analysis of patient fibroblasts carrying a deletion removing the MOCS2A start codon; transcript analysis confirming both mRNAs are present","journal":"Molecular genetics and metabolism","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Western blot with transcript analysis in patient-derived material, single lab","pmids":["16737835"],"is_preprint":false},{"year":2022,"finding":"The C. elegans ortholog of MOCS2A (K10D2.7/moc-6) is necessary for endogenous molybdenum cofactor synthesis, genetically demonstrating the conserved sulfur-carrier function of the MOCS2A subunit in vivo.","method":"CRISPR/Cas9 null allele generation in C. elegans; biochemical assessment of Moco synthesis in null mutants","journal":"microPublication biology","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — clean genetic knockout with defined biochemical phenotype, single lab, single study","pmids":["35224462"],"is_preprint":false},{"year":2025,"finding":"A variant affecting both overlapping reading frames of MOCS2 (p.Ile82Phe in MOCS2A / p.Leu19Phe in MOCS2B) significantly decreases molybdopterin (MPT) synthase complex formation and MPT synthesis activity in vitro, confirming that both subunit interactions and enzymatic activity are disrupted by this single nucleotide change.","method":"In vitro functional characterization of MPT synthesis activity and protein complex formation using recombinant proteins","journal":"European journal of pediatrics","confidence":"Medium","confidence_rationale":"Tier 1 / Weak — in vitro reconstitution assay with activity measurement, single lab","pmids":["40707723"],"is_preprint":false},{"year":2015,"finding":"The MOCS2B missense mutation p.S140F is pathogenic, as demonstrated by protein expression studies confirming disrupted protein function, placing MOCS2B activity as essential for molybdopterin synthase function.","method":"Protein expression studies in patient-derived material and in vitro characterization of the p.S140F variant","journal":"Meta gene","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single lab, protein expression study with limited mechanistic detail reported in abstract","pmids":["25709896"],"is_preprint":false}],"current_model":"MOCS2 encodes both subunits of molybdopterin (MPT) synthase — the small sulfur-carrier subunit MOCS2A and the large catalytic subunit MOCS2B — via two overlapping reading frames expressed from alternatively spliced transcripts; MOCS2A is required for MOCS2B protein stability, the C-terminus of MOCS2B mediates binding to both MOCS2A and the substrate precursor Z, and the intact heterodimeric complex is essential for converting precursor Z to molybdopterin in the conserved molybdenum cofactor biosynthesis pathway."},"narrative":{"mechanistic_narrative":"MOCS2 catalyzes the second step of the conserved molybdenum cofactor biosynthesis pathway, converting precursor Z to molybdopterin (MPT) as the molybdopterin synthase enzyme [PMID:12754701, PMID:16737835, PMID:40707723]. The gene has a bicistronic architecture, encoding two distinct proteins in overlapping reading frames — the small sulfur-carrier subunit MOCS2A and the large catalytic subunit MOCS2B — expressed either from alternatively spliced mRNAs or by independent translation of a bicistronic transcript [PMID:12754701, PMID:16737835]. The two subunits assemble into an obligate heterodimeric complex: the C-terminus of MOCS2B mediates binding to both the precursor Z substrate and to MOCS2A, and a mutation eliminating the MOCS2B stop codon abolishes both interactions [PMID:16021469], while MOCS2B protein is degraded in the absence of MOCS2A, establishing co-dependence of the subunits for stability [PMID:16737835]. A single nucleotide change disrupting both reading frames reduces MPT synthase complex formation and enzymatic activity, confirming that intact subunit assembly is required for catalysis [PMID:40707723]. The conserved sulfur-carrier role of the MOCS2A subunit in endogenous molybdenum cofactor synthesis has been validated genetically in the C. elegans ortholog moc-6 [PMID:35224462].","teleology":[{"year":2003,"claim":"Resolved how a single locus produces both subunits of an enzyme, establishing that MOCS2 uses a bicistronic, overlapping reading-frame architecture to encode MOCS2A and MOCS2B as the small and large subunits of molybdopterin synthase.","evidence":"Molecular cloning and alternative splicing/bicistronic mRNA characterization","pmids":["12754701","16737835"],"confidence":"High","gaps":["Relative stoichiometry and regulation of the two translation products not defined","Mechanism of independent translation versus splicing not resolved"]},{"year":2005,"claim":"Localized the substrate- and partner-binding determinants of the large subunit by showing that the MOCS2B C-terminus is required for binding both precursor Z and MOCS2A.","evidence":"In vitro expression of a stop-codon-loss mutant with precursor Z and MOCS2A binding assays","pmids":["16021469"],"confidence":"Medium","gaps":["Single lab; no structural model of the binding interface","Does not define MOCS2A catalytic contribution"]},{"year":2006,"claim":"Established subunit co-dependence by demonstrating that MOCS2B protein is degraded without MOCS2A even when both transcripts are produced normally.","evidence":"Western blot of patient fibroblasts with a MOCS2A start-codon deletion plus transcript analysis","pmids":["16737835"],"confidence":"Medium","gaps":["Degradation pathway for free MOCS2B not identified","Single patient-derived material, single lab"]},{"year":2015,"claim":"Linked a specific MOCS2B missense variant (p.S140F) to disrupted protein function, supporting that MOCS2B activity is essential for molybdopterin synthase function.","evidence":"Protein expression studies in patient-derived material and in vitro characterization","pmids":["25709896"],"confidence":"Low","gaps":["Limited mechanistic detail reported in abstract","Quantitative activity loss not characterized"]},{"year":2022,"claim":"Provided in vivo genetic confirmation of the MOCS2A sulfur-carrier function by showing the C. elegans ortholog moc-6 is required for endogenous molybdenum cofactor synthesis.","evidence":"CRISPR/Cas9 null allele in C. elegans with biochemical assessment of Moco synthesis","pmids":["35224462"],"confidence":"Medium","gaps":["Ortholog system; human MOCS2A in vivo requirement inferred","Biochemistry of sulfur transfer not directly addressed"]},{"year":2025,"claim":"Demonstrated that a single variant affecting both overlapping reading frames simultaneously impairs complex assembly and catalysis, directly coupling subunit interaction to enzymatic output.","evidence":"In vitro reconstitution of MPT synthesis activity and complex formation with recombinant proteins","pmids":["40707723"],"confidence":"Medium","gaps":["Single lab in vitro reconstitution","Separate contributions of the two reading-frame changes not deconvolved"]},{"year":null,"claim":"The structural basis of MOCS2A/MOCS2B heterodimer assembly, the sulfur-transfer chemistry of precursor Z conversion in the human enzyme, and the degradation pathway controlling MOCS2B stability remain uncharacterized in the available corpus.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No human structural model of the heterodimer","Sulfur-transfer mechanism not directly assayed","MOCS2B degradation machinery unidentified"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0016740","term_label":"transferase activity","supporting_discovery_ids":[0,4]},{"term_id":"GO:0016874","term_label":"ligase activity","supporting_discovery_ids":[4]}],"localization":[],"pathway":[{"term_id":"R-HSA-1430728","term_label":"Metabolism","supporting_discovery_ids":[0,3,4]}],"complexes":["molybdopterin synthase"],"partners":["MOCS2A","MOCS2B"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"O96007","full_name":"Molybdopterin synthase catalytic subunit","aliases":["MOCO1-B","Molybdenum cofactor synthesis protein 2 large subunit","Molybdenum cofactor synthesis protein 2B","MOCS2B","Molybdopterin-synthase large subunit","MPT synthase large subunit"],"length_aa":188,"mass_kda":20.9,"function":"Catalytic subunit of the molybdopterin synthase complex, a complex that catalyzes the conversion of precursor Z into molybdopterin. Acts by mediating the incorporation of 2 sulfur atoms from thiocarboxylated MOCS2A into precursor Z to generate a dithiolene group (By similarity) (PubMed:12732628, PubMed:15073332, PubMed:25709896). Together with MBIP, inhibits the activity of stress kinase EIF2AK2/PKR; this may suppress JNK activation and subsequent stress-responsive transcription, or suppress eIF2a phosphorylation to favor translation (PubMed:26705305)","subcellular_location":"Cytoplasm, cytosol; Nucleus","url":"https://www.uniprot.org/uniprotkb/O96007/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/MOCS2","classification":"Not Classified","n_dependent_lines":7,"n_total_lines":1208,"dependency_fraction":0.005794701986754967},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[{"gene":"IPO13","stoichiometry":0.2},{"gene":"MAP2K7","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/search/MOCS2","total_profiled":1310},"omim":[{"mim_id":"621373","title":"MOLYBDENUM COFACTOR DEFICIENCY, TYPE B2; MOCODB2","url":"https://www.omim.org/entry/621373"},{"mim_id":"615501","title":"MOLYBDENUM COFACTOR DEFICIENCY, TYPE C; MOCODC","url":"https://www.omim.org/entry/615501"},{"mim_id":"603930","title":"GEPHYRIN; GPHN","url":"https://www.omim.org/entry/603930"},{"mim_id":"603708","title":"MOLYBDENUM COFACTOR SYNTHESIS GENE 2; MOCS2","url":"https://www.omim.org/entry/603708"},{"mim_id":"603707","title":"MOLYBDENUM COFACTOR SYNTHESIS GENE 1; MOCS1","url":"https://www.omim.org/entry/603707"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Cytosol","reliability":"Supported"},{"location":"Nucleoplasm","reliability":"Additional"},{"location":"Nuclear speckles","reliability":"Additional"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/MOCS2"},"hgnc":{"alias_symbol":["MOCO1","MOCS2A","MOCS2B"],"prev_symbol":[]},"alphafold":{"accession":"O96007","domains":[{"cath_id":"3.90.1170.40","chopping":"43-169","consensus_level":"high","plddt":98.2144,"start":43,"end":169}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/O96007","model_url":"https://alphafold.ebi.ac.uk/files/AF-O96007-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-O96007-F1-predicted_aligned_error_v6.png","plddt_mean":84.0},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=MOCS2","jax_strain_url":"https://www.jax.org/strain/search?query=MOCS2"},"sequence":{"accession":"O96007","fasta_url":"https://rest.uniprot.org/uniprotkb/O96007.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/O96007/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/O96007"}},"corpus_meta":[{"pmid":"21031595","id":"PMC_21031595","title":"Molybdenum cofactor deficiency: Mutations in GPHN, MOCS1, and MOCS2.","date":"2011","source":"Human mutation","url":"https://pubmed.ncbi.nlm.nih.gov/21031595","citation_count":106,"is_preprint":false},{"pmid":"12754701","id":"PMC_12754701","title":"Mutations in the molybdenum cofactor biosynthetic genes MOCS1, MOCS2, and GEPH.","date":"2003","source":"Human mutation","url":"https://pubmed.ncbi.nlm.nih.gov/12754701","citation_count":99,"is_preprint":false},{"pmid":"16021469","id":"PMC_16021469","title":"Ten novel mutations in the molybdenum cofactor genes MOCS1 and MOCS2 and in vitro characterization of a MOCS2 mutation that abolishes the binding ability of molybdopterin synthase.","date":"2005","source":"Human genetics","url":"https://pubmed.ncbi.nlm.nih.gov/16021469","citation_count":22,"is_preprint":false},{"pmid":"31201073","id":"PMC_31201073","title":"The Clinical and Molecular Characteristics of Molybdenum Cofactor Deficiency Due to MOCS2 Mutations.","date":"2019","source":"Pediatric neurology","url":"https://pubmed.ncbi.nlm.nih.gov/31201073","citation_count":16,"is_preprint":false},{"pmid":"16737835","id":"PMC_16737835","title":"A novel MOCS2 mutation reveals coordinated expression of the small and large subunit of molybdopterin synthase.","date":"2006","source":"Molecular genetics and metabolism","url":"https://pubmed.ncbi.nlm.nih.gov/16737835","citation_count":16,"is_preprint":false},{"pmid":"25709896","id":"PMC_25709896","title":"Investigation of molybdenum cofactor deficiency due to MOCS2 deficiency in a newborn baby.","date":"2015","source":"Meta gene","url":"https://pubmed.ncbi.nlm.nih.gov/25709896","citation_count":14,"is_preprint":false},{"pmid":"35224462","id":"PMC_35224462","title":"moc-6/MOCS2A is necessary for molybdenum cofactor synthesis in C. elegans.","date":"2022","source":"microPublication biology","url":"https://pubmed.ncbi.nlm.nih.gov/35224462","citation_count":7,"is_preprint":false},{"pmid":"35744859","id":"PMC_35744859","title":"Beyond Moco Biosynthesis-Moonlighting Roles of MoaE and MOCS2.","date":"2022","source":"Molecules (Basel, Switzerland)","url":"https://pubmed.ncbi.nlm.nih.gov/35744859","citation_count":3,"is_preprint":false},{"pmid":"33066491","id":"PMC_33066491","title":"Proteins Structure Models in the Evaluation of Novel Variant (C.472_477del) in the MOCS2 Gene.","date":"2020","source":"Diagnostics (Basel, Switzerland)","url":"https://pubmed.ncbi.nlm.nih.gov/33066491","citation_count":3,"is_preprint":false},{"pmid":"34674206","id":"PMC_34674206","title":"Genotype-Phenotype Dissociation in Two Taiwanese Children with Molybdenum Cofactor Deficiency Caused by MOCS2 Mutation.","date":"2021","source":"Neuropediatrics","url":"https://pubmed.ncbi.nlm.nih.gov/34674206","citation_count":3,"is_preprint":false},{"pmid":"40707723","id":"PMC_40707723","title":"A prevalent MOCS2 variant in the Roma population is associated with a novel mild form of molybdenum cofactor deficiency.","date":"2025","source":"European journal of pediatrics","url":"https://pubmed.ncbi.nlm.nih.gov/40707723","citation_count":2,"is_preprint":false},{"pmid":"36980992","id":"PMC_36980992","title":"Live Birth of a Healthy Child in a Couple with Identical mtDNA Carrying a Pathogenic c.471_477delTTTAAAAinsG Variant in the MOCS2 Gene.","date":"2023","source":"Genes","url":"https://pubmed.ncbi.nlm.nih.gov/36980992","citation_count":1,"is_preprint":false},{"pmid":"39400946","id":"PMC_39400946","title":"Exome Sequencing of Consanguineous Pashtun Families With Familial Epilepsy Reveals Causative and Candidate Variants in TSEN54, MOCS2, and OPHN1.","date":"2024","source":"Clinical genetics","url":"https://pubmed.ncbi.nlm.nih.gov/39400946","citation_count":1,"is_preprint":false},{"pmid":"41731370","id":"PMC_41731370","title":"Two mild phenotype molybdenum cofactor deficiency patients with novel MOCS2 mutation and immunological treatment after COVID-19 infection.","date":"2026","source":"BMC neurology","url":"https://pubmed.ncbi.nlm.nih.gov/41731370","citation_count":0,"is_preprint":false},{"pmid":"39005576","id":"PMC_39005576","title":"A case report of MoCD etiology in a neonate: A novel homozygous MoCS2 variant.","date":"2024","source":"Clinical case reports","url":"https://pubmed.ncbi.nlm.nih.gov/39005576","citation_count":0,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":9231,"output_tokens":1380,"usd":0.024196,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":8074,"output_tokens":2128,"usd":0.046785,"stage2_stop_reason":"end_turn"},"total_usd":0.070981,"stage1_batch_id":"msgbatch_01BbTCMyrRPyhtEq6b1MdwCN","stage2_batch_id":"msgbatch_011dEed5bbxYvTAaQWKJevxu","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2003,\n      \"finding\": \"MOCS2 has a bicistronic architecture encoding two proteins (MOCS2A and MOCS2B) in different, overlapping open reading frames. These proteins are expressed either from different mRNAs generated by alternative splicing or by independent translation of a bicistronic mRNA, forming the small and large subunits of molybdopterin synthase respectively.\",\n      \"method\": \"Molecular cloning, alternative splicing analysis, bicistronic mRNA characterization\",\n      \"journal\": \"Human mutation\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — independently replicated across multiple labs and papers, confirmed by experimental expression studies and functional characterization\",\n      \"pmids\": [\"12754701\", \"16737835\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"A MOCS2B mutation that eliminates the stop codon (elongating the large subunit) abolishes the binding affinity of MOCS2B for both precursor Z (the substrate) and the small subunit MOCS2A, demonstrating that the C-terminus of MOCS2B is required for substrate binding and subunit interaction.\",\n      \"method\": \"In vitro expression of mutant protein, binding assay for precursor Z and MOCS2A interaction\",\n      \"journal\": \"Human genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct in vitro binding assay with mutagenesis, single lab\",\n      \"pmids\": [\"16021469\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"MOCS2B (large subunit of molybdopterin synthase) is unstable in the absence of MOCS2A (small subunit), revealing that the two subunits are co-dependent for protein stability; both transcripts are produced normally from a deletion removing the MOCS2A start codon, but MOCS2B protein is degraded without its partner.\",\n      \"method\": \"Western blot analysis of patient fibroblasts carrying a deletion removing the MOCS2A start codon; transcript analysis confirming both mRNAs are present\",\n      \"journal\": \"Molecular genetics and metabolism\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Western blot with transcript analysis in patient-derived material, single lab\",\n      \"pmids\": [\"16737835\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"The C. elegans ortholog of MOCS2A (K10D2.7/moc-6) is necessary for endogenous molybdenum cofactor synthesis, genetically demonstrating the conserved sulfur-carrier function of the MOCS2A subunit in vivo.\",\n      \"method\": \"CRISPR/Cas9 null allele generation in C. elegans; biochemical assessment of Moco synthesis in null mutants\",\n      \"journal\": \"microPublication biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — clean genetic knockout with defined biochemical phenotype, single lab, single study\",\n      \"pmids\": [\"35224462\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"A variant affecting both overlapping reading frames of MOCS2 (p.Ile82Phe in MOCS2A / p.Leu19Phe in MOCS2B) significantly decreases molybdopterin (MPT) synthase complex formation and MPT synthesis activity in vitro, confirming that both subunit interactions and enzymatic activity are disrupted by this single nucleotide change.\",\n      \"method\": \"In vitro functional characterization of MPT synthesis activity and protein complex formation using recombinant proteins\",\n      \"journal\": \"European journal of pediatrics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Weak — in vitro reconstitution assay with activity measurement, single lab\",\n      \"pmids\": [\"40707723\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"The MOCS2B missense mutation p.S140F is pathogenic, as demonstrated by protein expression studies confirming disrupted protein function, placing MOCS2B activity as essential for molybdopterin synthase function.\",\n      \"method\": \"Protein expression studies in patient-derived material and in vitro characterization of the p.S140F variant\",\n      \"journal\": \"Meta gene\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single lab, protein expression study with limited mechanistic detail reported in abstract\",\n      \"pmids\": [\"25709896\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"MOCS2 encodes both subunits of molybdopterin (MPT) synthase — the small sulfur-carrier subunit MOCS2A and the large catalytic subunit MOCS2B — via two overlapping reading frames expressed from alternatively spliced transcripts; MOCS2A is required for MOCS2B protein stability, the C-terminus of MOCS2B mediates binding to both MOCS2A and the substrate precursor Z, and the intact heterodimeric complex is essential for converting precursor Z to molybdopterin in the conserved molybdenum cofactor biosynthesis pathway.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"MOCS2 catalyzes the second step of the conserved molybdenum cofactor biosynthesis pathway, converting precursor Z to molybdopterin (MPT) as the molybdopterin synthase enzyme [#0, #4]. The gene has a bicistronic architecture, encoding two distinct proteins in overlapping reading frames \\u2014 the small sulfur-carrier subunit MOCS2A and the large catalytic subunit MOCS2B \\u2014 expressed either from alternatively spliced mRNAs or by independent translation of a bicistronic transcript [#0]. The two subunits assemble into an obligate heterodimeric complex: the C-terminus of MOCS2B mediates binding to both the precursor Z substrate and to MOCS2A, and a mutation eliminating the MOCS2B stop codon abolishes both interactions [#1], while MOCS2B protein is degraded in the absence of MOCS2A, establishing co-dependence of the subunits for stability [#2]. A single nucleotide change disrupting both reading frames reduces MPT synthase complex formation and enzymatic activity, confirming that intact subunit assembly is required for catalysis [#4]. The conserved sulfur-carrier role of the MOCS2A subunit in endogenous molybdenum cofactor synthesis has been validated genetically in the C. elegans ortholog moc-6 [#3].\",\n  \"teleology\": [\n    {\n      \"year\": 2003,\n      \"claim\": \"Resolved how a single locus produces both subunits of an enzyme, establishing that MOCS2 uses a bicistronic, overlapping reading-frame architecture to encode MOCS2A and MOCS2B as the small and large subunits of molybdopterin synthase.\",\n      \"evidence\": \"Molecular cloning and alternative splicing/bicistronic mRNA characterization\",\n      \"pmids\": [\"12754701\", \"16737835\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Relative stoichiometry and regulation of the two translation products not defined\", \"Mechanism of independent translation versus splicing not resolved\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Localized the substrate- and partner-binding determinants of the large subunit by showing that the MOCS2B C-terminus is required for binding both precursor Z and MOCS2A.\",\n      \"evidence\": \"In vitro expression of a stop-codon-loss mutant with precursor Z and MOCS2A binding assays\",\n      \"pmids\": [\"16021469\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single lab; no structural model of the binding interface\", \"Does not define MOCS2A catalytic contribution\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Established subunit co-dependence by demonstrating that MOCS2B protein is degraded without MOCS2A even when both transcripts are produced normally.\",\n      \"evidence\": \"Western blot of patient fibroblasts with a MOCS2A start-codon deletion plus transcript analysis\",\n      \"pmids\": [\"16737835\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Degradation pathway for free MOCS2B not identified\", \"Single patient-derived material, single lab\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Linked a specific MOCS2B missense variant (p.S140F) to disrupted protein function, supporting that MOCS2B activity is essential for molybdopterin synthase function.\",\n      \"evidence\": \"Protein expression studies in patient-derived material and in vitro characterization\",\n      \"pmids\": [\"25709896\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"Limited mechanistic detail reported in abstract\", \"Quantitative activity loss not characterized\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Provided in vivo genetic confirmation of the MOCS2A sulfur-carrier function by showing the C. elegans ortholog moc-6 is required for endogenous molybdenum cofactor synthesis.\",\n      \"evidence\": \"CRISPR/Cas9 null allele in C. elegans with biochemical assessment of Moco synthesis\",\n      \"pmids\": [\"35224462\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Ortholog system; human MOCS2A in vivo requirement inferred\", \"Biochemistry of sulfur transfer not directly addressed\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Demonstrated that a single variant affecting both overlapping reading frames simultaneously impairs complex assembly and catalysis, directly coupling subunit interaction to enzymatic output.\",\n      \"evidence\": \"In vitro reconstitution of MPT synthesis activity and complex formation with recombinant proteins\",\n      \"pmids\": [\"40707723\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single lab in vitro reconstitution\", \"Separate contributions of the two reading-frame changes not deconvolved\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"The structural basis of MOCS2A/MOCS2B heterodimer assembly, the sulfur-transfer chemistry of precursor Z conversion in the human enzyme, and the degradation pathway controlling MOCS2B stability remain uncharacterized in the available corpus.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No human structural model of the heterodimer\", \"Sulfur-transfer mechanism not directly assayed\", \"MOCS2B degradation machinery unidentified\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0016740\", \"supporting_discovery_ids\": [0, 4]},\n      {\"term_id\": \"GO:0016874\", \"supporting_discovery_ids\": [4]}\n    ],\n    \"localization\": [],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-1430728\", \"supporting_discovery_ids\": [0, 3, 4]}\n    ],\n    \"complexes\": [\"molybdopterin synthase\"],\n    \"partners\": [\"MOCS2A\", \"MOCS2B\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":5,"faith_total":5,"faith_pct":100.0}}