{"id":"2221777f-171d-5b97-9739-14b08df0d110","stable_key":"dc8975b1-95ff-5d9b-be17-a1c04610cca7:mo-mocs2a-sulfur","predicate":"supplies_sulfur_for","statement":"The sulfur used to form the MPT dithiolene group is supplied from the C-terminal thiocarboxylate of the small MPT-synthase subunit.","claim_class":"mechanistic","status":"source_derived_draft","evidence_grade":"ungraded","direction":"context_dependent","is_public":true,"mechanism_event_id":"a1d2abd7-3da4-5269-bf83-7c6e7d3f8d04","mechanism_event_label":"MOCS2A carries a chemically attached sulfur supply.","subject":{"id":"40d8c40b-e0a1-59b7-b994-3d1d520987f9","slug":"mocs2a-thiocarboxylate","display_name":"Human MOCS2A C-terminal thiocarboxylate","entity_type_key":"protein_state"},"object":{"id":"368ffa4f-299e-5783-918e-452785c0bfbd","slug":"molybdopterin","display_name":"Metal-free molybdopterin / MPT","entity_type_key":"small_molecule"},"evidence_count":1,"mechanism_event":{"id":"a1d2abd7-3da4-5269-bf83-7c6e7d3f8d04","stable_key":"dc8975b1-95ff-5d9b-be17-a1c04610cca7:mo-mocs2a-sulfur-event","event_type":"biochemical_relationship","label":"MOCS2A carries a chemically attached sulfur supply.","description":"The sulfur used to form the MPT dithiolene group is supplied from the C-terminal thiocarboxylate of the small MPT-synthase subunit.","status":"provisional","compartment":null,"participants":[{"entity":{"id":"40d8c40b-e0a1-59b7-b994-3d1d520987f9","slug":"mocs2a-thiocarboxylate","display_name":"Human MOCS2A C-terminal thiocarboxylate","entity_type_key":"protein_state"},"role":"subject","stoichiometry":null,"state_label":"","sequence_order":0,"notes":""},{"entity":{"id":"368ffa4f-299e-5783-918e-452785c0bfbd","slug":"molybdopterin","display_name":"Metal-free molybdopterin / MPT","entity_type_key":"small_molecule"},"role":"target","stoichiometry":null,"state_label":"","sequence_order":1,"notes":""}]},"contexts":[{"dimension":"evidence_span","value_text":"{\"source_cache\": \"artifacts/molybdenum-research/12732628.abstract.txt\", \"locator\": \"Exact primary indexed abstract; zero-based, end-exclusive Unicode character offsets\", \"file_sha256\": \"154da4e4528674556bef92dfe50f098cfd9ae715c06ea01fc17d64c64b8aa319\", \"start_char\": 0, \"end_char\": 1322, \"text_sha256\": \"154da4e4528674556bef92dfe50f098cfd9ae715c06ea01fc17d64c64b8aa319\"}","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"experimental_model","value_text":"Purified human MPT synthase and patient-derived point mutants","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"exposure","value_text":"Precursor Z/cPMP conversion assays","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"limitations","value_text":"In-vitro assembly and kinetic defects; severity comparisons refer to specific patients, not a universal hierarchy.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"nutrient_topic","value_text":"Molybdenum research collection; topical membership is not evidence of a direct dietary effect.","comparator":null,"unit":null,"notes":"","entity":{"slug":"molybdenum","display_name":"Molybdenum","entity_type_key":"nutrient_element"}},{"dimension":"organism","value_text":"Human proteins expressed in Escherichia coli","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"plain_language","value_text":"MOCS2A carries a chemically attached sulfur supply.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"primary_references","value_text":"[mo-p12732628] Mechanistic studies of human molybdopterin synthase reaction and characterization of mutants identified in group B patients of molybdenum cofactor deficiency. (2003). https://pubmed.ncbi.nlm.nih.gov/12732628/ DOI: 10.1074/jbc.m303092200","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"tissue_or_cell_type","value_text":"Reconstituted MOCS2A/MOCS2B tetramers","comparator":null,"unit":null,"notes":"","entity":null}],"evidence":[{"id":"6fc6489d-8935-5302-9e67-20a1ed51d738","evidence_kind":"source_excerpt","locator":"Lines 404-415","start_line":404,"end_line":415,"excerpt":"### mo-mocs2a-sulfur\nThe sulfur used to form the MPT dithiolene group is supplied from the C-terminal thiocarboxylate of the small MPT-synthase subunit.\nCondition category: normal\nnutrient_topic: Molybdenum research collection; topical membership is not evidence of a direct dietary effect.\nplain_language: MOCS2A carries a chemically attached sulfur supply.\norganism: Human proteins expressed in Escherichia coli\ntissue_or_cell_type: Reconstituted MOCS2A/MOCS2B tetramers\nexperimental_model: Purified human MPT synthase and patient-derived point mutants\nlimitations: In-vitro assembly and kinetic defects; severity comparisons refer to specific patients, not a universal hierarchy.\nexposure: Precursor Z/cPMP conversion assays\nevidence_span: {\"source_cache\": \"artifacts/molybdenum-research/12732628.abstract.txt\", \"locator\": \"Exact primary indexed abstract; zero-based, end-exclusive Unicode character offsets\", \"file_sha256\": \"154da4e4528674556bef92dfe50f098cfd9ae715c06ea01fc17d64c64b8aa319\", \"start_char\": 0, \"end_char\": 1322, \"text_sha256\": \"154da4e4528674556bef92dfe50f098cfd9ae715c06ea01fc17d64c64b8aa319\"}\n[mo-p12732628] Mechanistic studies of human molybdopterin synthase reaction and characterization of mutants identified in group B patients of molybdenum cofactor deficiency. (2003). https://pubmed.ncbi.nlm.nih.gov/12732628/ DOI: 10.1074/jbc.m303092200","model_system":"Purified human MPT synthase and patient-derived point mutants","directness":"author_interpretation","verification_status":"source_derived_draft","notes":"Exact curation-document quotation, not publisher quotation. Study references: [mo-p12732628] Mechanistic studies of human molybdopterin synthase reaction and characterization of mutants identified in group B patients of molybdenum cofactor deficiency. (2003). https://pubmed.ncbi.nlm.nih.gov/12732628/ DOI: 10.1074/jbc.m303092200","relationship":"supports","weight":1.0,"link_notes":"","source":{"id":"1aa6da60-8284-5252-8dd9-ac2250d5ced5","stable_key":"import-dc8975b1-95ff-5d9b-be17-a1c04610cca7","title":"Molybdenum: cofactor assembly, sulfur metabolism and nutrient interactions (2026-09-17)","document_type":"imported_text","citation_label":"AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. 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