{"id":"5f6c3e0c-2475-579f-9525-4f09e8afa1a8","stable_key":"08ce9896-9d1c-5bbf-b705-5bfe771091d5:b7-pc-tetramer","predicate":"has_tetramerization_architecture","statement":"The human PC C-terminal structure displayed a conserved tetrameric arrangement, with a PC tetramerization domain identified by structural and mutagenesis analysis.","claim_class":"mechanistic","status":"source_derived_draft","evidence_grade":"ungraded","direction":"context_dependent","is_public":true,"mechanism_event_id":"2b8edef4-5486-5148-a89b-6ec867740a19","mechanism_event_label":"Enzyme assembly matters as well as the availability of biotin.","subject":{"id":"b84a1471-7246-543a-8f35-2bedbca6bf0b","slug":"pc","display_name":"Human pyruvate carboxylase / PC","entity_type_key":"protein"},"object":{"id":"b84a1471-7246-543a-8f35-2bedbca6bf0b","slug":"pc","display_name":"Human pyruvate carboxylase / PC","entity_type_key":"protein"},"evidence_count":1,"mechanism_event":{"id":"2b8edef4-5486-5148-a89b-6ec867740a19","stable_key":"08ce9896-9d1c-5bbf-b705-5bfe771091d5:b7-pc-tetramer-event","event_type":"biochemical_relationship","label":"Enzyme assembly matters as well as the availability of biotin.","description":"The human PC C-terminal structure displayed a conserved tetrameric arrangement, with a PC tetramerization domain identified by structural and mutagenesis analysis.","status":"provisional","compartment":null,"participants":[{"entity":{"id":"37a8e96b-f95b-5ba7-a0bc-8ed3cfaf5fd8","slug":"biotin","display_name":"Biotin","entity_type_key":"small_molecule"},"role":"carrier-domain cofactor","stoichiometry":null,"state_label":"","sequence_order":0,"notes":""},{"entity":{"id":"b84a1471-7246-543a-8f35-2bedbca6bf0b","slug":"pc","display_name":"Human pyruvate carboxylase / PC","entity_type_key":"protein"},"role":"subject","stoichiometry":null,"state_label":"","sequence_order":1,"notes":""}]},"contexts":[{"dimension":"evidence_span","value_text":"{\"source_cache\": \"artifacts/biotin-research/18297087.abstract.txt\", \"locator\": \"Exact primary indexed abstract; zero-based, end-exclusive Unicode character offsets\", \"file_sha256\": \"64ad42b855e8e31bb8103ad2740baab36988d47779218fbbf19b13f34f4a4d10\", \"start_char\": 0, \"end_char\": 1026, \"text_sha256\": \"64ad42b855e8e31bb8103ad2740baab36988d47779218fbbf19b13f34f4a4d10\"}","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"experimental_model","value_text":"Crystal structures of human PC lacking the BC domain and full-length S. aureus PC; mutagenesis","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"exposure","value_text":"Structural and mutagenesis experiments","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"limitations","value_text":"The human structure was a C-terminal fragment, not intact human PC; bacterial domain positions must not be silently assigned to human enzyme.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"nutrient_topic","value_text":"Biotin research collection; topical membership is not evidence of a direct dietary effect.","comparator":null,"unit":null,"notes":"","entity":{"slug":"biotin","display_name":"Biotin","entity_type_key":"small_molecule"}},{"dimension":"organism","value_text":"Homo sapiens; Staphylococcus aureus","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"plain_language","value_text":"Enzyme assembly matters as well as the availability of biotin.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"primary_references","value_text":"[b7-p18297087] Crystal structures of human and Staphylococcus aureus pyruvate carboxylase and molecular insights into the carboxyltransfer reaction. 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(2008). https://pubmed.ncbi.nlm.nih.gov/18297087/ DOI: 10.1038/nsmb.1393","model_system":"Crystal structures of human PC lacking the BC domain and full-length S. aureus PC; mutagenesis","directness":"author_interpretation","verification_status":"source_derived_draft","notes":"Exact curation-document quotation, not publisher quotation. Study references: [b7-p18297087] Crystal structures of human and Staphylococcus aureus pyruvate carboxylase and molecular insights into the carboxyltransfer reaction. (2008). https://pubmed.ncbi.nlm.nih.gov/18297087/ DOI: 10.1038/nsmb.1393","relationship":"supports","weight":1.0,"link_notes":"","source":{"id":"9608806b-adb6-5a35-b042-057147135642","stable_key":"import-08ce9896-9d1c-5bbf-b705-5bfe771091d5","title":"Biotin: carboxylases, recycling, deficiency 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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