{"id":"1f662d71-45cb-5703-b75e-ec9970dca124","stable_key":"548ab9d6-3a9b-5bed-879c-17d03813b636:b2-met-porcine-etfdh-cofactors","predicate":"binds-distinct-redox-cofactors","statement":"Porcine ETF-QO crystal structures resolved one FAD and one [4Fe-4S] cluster per protein, together with a separate ubiquinone-binding region.","claim_class":"mechanistic","status":"source_derived_draft","evidence_grade":"ungraded","direction":"positive","is_public":true,"mechanism_event_id":"b1642f64-89d9-5e38-855c-683d2ffd5987","mechanism_event_label":"ETF-QO combines flavin and iron-sulfur chemistry in one protein downstream of ETF.","subject":{"id":"a8bfdf40-33a7-51c0-9e12-5259d69b94fd","slug":"porcine-etfdh","display_name":"Porcine electron transfer flavoprotein dehydrogenase","entity_type_key":"protein"},"object":{"id":"e2cd7179-f218-54e8-9ce9-7a836ae35fac","slug":"fad","display_name":"FAD","entity_type_key":"small_molecule"},"evidence_count":1,"mechanism_event":{"id":"b1642f64-89d9-5e38-855c-683d2ffd5987","stable_key":"548ab9d6-3a9b-5bed-879c-17d03813b636:b2-met-porcine-etfdh-cofactors-event","event_type":"biochemical_relationship","label":"ETF-QO combines flavin and iron-sulfur chemistry in one protein downstream of ETF.","description":"Porcine ETF-QO crystal structures resolved one FAD and one [4Fe-4S] cluster per protein, together with a separate ubiquinone-binding region.","status":"provisional","compartment":{"slug":"mitochondria","display_name":"Mitochondria"},"participants":[{"entity":{"id":"8058ae47-b091-5004-ba65-1e50ad91f70b","slug":"iron-sulfur-4fe4s","display_name":"[4Fe-4S] iron-sulfur cluster","entity_type_key":"chemical_species"},"role":"separate redox cofactor","stoichiometry":null,"state_label":"","sequence_order":0,"notes":""},{"entity":{"id":"ae9544c3-df78-54f8-80e7-5b643e5ba1cf","slug":"ubiquinone","display_name":"Ubiquinone","entity_type_key":"small_molecule"},"role":"bound quinone","stoichiometry":null,"state_label":"","sequence_order":1,"notes":""},{"entity":{"id":"89bcaf42-b4ab-5760-8c2e-44eace10cee0","slug":"iron","display_name":"Iron","entity_type_key":"nutrient_element"},"role":"element in cluster","stoichiometry":null,"state_label":"","sequence_order":2,"notes":""},{"entity":{"id":"a8bfdf40-33a7-51c0-9e12-5259d69b94fd","slug":"porcine-etfdh","display_name":"Porcine electron transfer flavoprotein dehydrogenase","entity_type_key":"protein"},"role":"subject","stoichiometry":null,"state_label":"","sequence_order":3,"notes":""},{"entity":{"id":"e2cd7179-f218-54e8-9ce9-7a836ae35fac","slug":"fad","display_name":"FAD","entity_type_key":"small_molecule"},"role":"target","stoichiometry":null,"state_label":"","sequence_order":4,"notes":""}]},"contexts":[{"dimension":"cross_nutrient","value_text":"B2-derived FAD and iron-containing cluster are distinct required molecular components; this does not establish supplement interactions.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"evidence_spans","value_text":"[{\"source_bundle\": \"artifacts/riboflavin_metabolism_sources.json\", \"source_key\": \"PMC1637562\", \"locator\": \"HTML article p\", \"paragraph_index\": 10, \"char_start\": 0, \"char_end\": 3701, \"evidence_access\": \"full-text\"}]","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"experimental_model","value_text":"Purified porcine ETF-QO crystal structures with and without bound ubiquinone.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"exposure","value_text":"No nutrient intervention; structural or biochemical characterization.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"limitations","value_text":"Static structure; the exact electron-entry sequence required additional functional experiments.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"nutrient_topic","value_text":"Riboflavin research collection; topical membership is not evidence of a direct dietary effect.","comparator":null,"unit":null,"notes":"","entity":{"slug":"riboflavin","display_name":"Riboflavin (vitamin B2)","entity_type_key":"small_molecule"}},{"dimension":"organism","value_text":"Sus scrofa","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"plain_language","value_text":"ETF-QO combines flavin and iron-sulfur chemistry in one protein downstream of ETF.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"primary_references","value_text":"[zhang-2006-etf-qo] Structure of electron transfer flavoprotein-ubiquinone oxidoreductase and electron transfer to the mitochondrial ubiquinone pool (2006). https://pubmed.ncbi.nlm.nih.gov/17050691/ DOI: 10.1073/pnas.0604567103","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"tissue_or_cell_type","value_text":"Purified porcine mitochondrial ETF-QO","comparator":null,"unit":null,"notes":"","entity":null}],"evidence":[{"id":"42ab1ee8-10cb-5b84-9c70-8c931c1df97b","evidence_kind":"source_excerpt","locator":"Lines 767-779","start_line":767,"end_line":779,"excerpt":"### b2-met-porcine-etfdh-cofactors\nPorcine ETF-QO crystal structures resolved one FAD and one [4Fe-4S] cluster per protein, together with a separate ubiquinone-binding region.\nCondition category: normal\nnutrient_topic: Riboflavin research collection; topical membership is not evidence of a direct dietary effect.\nplain_language: ETF-QO combines flavin and iron-sulfur chemistry in one protein downstream of ETF.\norganism: Sus scrofa\ntissue_or_cell_type: Purified porcine mitochondrial ETF-QO\nexperimental_model: Purified porcine ETF-QO crystal structures with and without bound ubiquinone.\nlimitations: Static structure; the exact electron-entry sequence required additional functional experiments.\nexposure: No nutrient intervention; structural or biochemical characterization.\ncross_nutrient: B2-derived FAD and iron-containing cluster are distinct required molecular components; this does not establish supplement interactions.\nevidence_spans: [{\"source_bundle\": \"artifacts/riboflavin_metabolism_sources.json\", \"source_key\": \"PMC1637562\", \"locator\": \"HTML article p\", \"paragraph_index\": 10, \"char_start\": 0, \"char_end\": 3701, \"evidence_access\": \"full-text\"}]\n[zhang-2006-etf-qo] Structure of electron transfer flavoprotein-ubiquinone oxidoreductase and electron transfer to the mitochondrial ubiquinone pool (2006). https://pubmed.ncbi.nlm.nih.gov/17050691/ DOI: 10.1073/pnas.0604567103","model_system":"Purified porcine ETF-QO crystal structures with and without bound ubiquinone.","directness":"author_interpretation","verification_status":"source_derived_draft","notes":"Exact curation-document quotation, not publisher quotation. Study references: [zhang-2006-etf-qo] Structure of electron transfer flavoprotein-ubiquinone oxidoreductase and electron transfer to the mitochondrial ubiquinone pool (2006). https://pubmed.ncbi.nlm.nih.gov/17050691/ DOI: 10.1073/pnas.0604567103","relationship":"supports","weight":1.0,"link_notes":"","source":{"id":"4f7c9578-82bf-5e2d-b5c4-72a79fb4f6af","stable_key":"import-548ab9d6-3a9b-5bed-879c-17d03813b636","title":"Riboflavin: mechanisms, 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. Not publisher full text.","file_path":"","sha256":"680cb6bc8249877f2410f551807f10d390fdd719014137d7414ba3420e29228d","revision_id":"7a61e299-908d-5372-860b-99ed190f9d7a","review_status":"unverified_draft","notes":""}}],"relations":[],"conflicts":[],"corrections":[],"research":null}