{"id":"1f9de9c2-e2eb-5ef3-9daa-29959cf3b1b2","stable_key":"0f17db03-207f-5910-ac8e-13dfc2f378ce:mg-bckdh-potassium-site","predicate":"supports","statement":"Human E1b contains potassium sites, including one organizing a loop near the ThDP cofactor.","claim_class":"mechanistic","status":"source_derived_draft","evidence_grade":"ungraded","direction":"positive","is_public":true,"mechanism_event_id":"03b72f78-d6b7-5f4d-96ec-af6928e51378","mechanism_event_label":"Potassium also helps shape this B1-dependent enzyme; the metal roles are distinct.","subject":{"id":"5dd31e52-f51e-51f3-880e-240abcc0ab1d","slug":"potassium-ion","display_name":"Potassium ion","entity_type_key":"ion"},"object":{"id":"82b74ccc-3ee5-5622-a8bd-0691de8cdc54","slug":"bckdh-e1","display_name":"Human branched-chain ketoacid dehydrogenase E1","entity_type_key":"protein_complex"},"evidence_count":1,"mechanism_event":{"id":"03b72f78-d6b7-5f4d-96ec-af6928e51378","stable_key":"0f17db03-207f-5910-ac8e-13dfc2f378ce:mg-bckdh-potassium-site-event","event_type":"biochemical_relationship","label":"Potassium also helps shape this B1-dependent enzyme; the metal roles are distinct.","description":"Human E1b contains potassium sites, including one organizing a loop near the ThDP cofactor.","status":"provisional","compartment":null,"participants":[{"entity":{"id":"187db168-8028-5ce6-9f8b-4bc61ebad1a0","slug":"thiamine-diphosphate","display_name":"Thiamine diphosphate","entity_type_key":"small_molecule"},"role":"nearby cofactor","stoichiometry":null,"state_label":"","sequence_order":0,"notes":""},{"entity":{"id":"bff427ab-35f9-59c2-bb24-fd5953bbaec2","slug":"magnesium-ion","display_name":"Mg2+","entity_type_key":"ion"},"role":"separate bound metal","stoichiometry":null,"state_label":"","sequence_order":1,"notes":""},{"entity":{"id":"5dd31e52-f51e-51f3-880e-240abcc0ab1d","slug":"potassium-ion","display_name":"Potassium ion","entity_type_key":"ion"},"role":"subject","stoichiometry":null,"state_label":"","sequence_order":2,"notes":""},{"entity":{"id":"82b74ccc-3ee5-5622-a8bd-0691de8cdc54","slug":"bckdh-e1","display_name":"Human branched-chain ketoacid dehydrogenase E1","entity_type_key":"protein_complex"},"role":"target","stoichiometry":null,"state_label":"","sequence_order":3,"notes":""}]},"contexts":[{"dimension":"cross_nutrient","value_text":"Potassium and magnesium contribute distinct sites in a thiamine-dependent branched-chain ketoacid enzyme.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"experimental_model","value_text":"Human E1b crystallography, deposited structure 1DTW.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"limitations","value_text":"A structural potassium site is not a potassium-intake response experiment.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"nutrient_topic","value_text":"Magnesium research collection; topical membership is not evidence of a direct dietary effect.","comparator":null,"unit":null,"notes":"","entity":{"slug":"magnesium","display_name":"Magnesium","entity_type_key":"nutrient_element"}},{"dimension":"organism","value_text":"Homo sapiens","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"plain_language","value_text":"Potassium also helps shape this B1-dependent enzyme; the metal roles are distinct.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"primary_references","value_text":"[aevarsson-2000-bckdh] Crystal structure of human branched-chain alpha-ketoacid dehydrogenase and the molecular basis of multienzyme complex deficiency in maple syrup urine disease (2000). https://pubmed.ncbi.nlm.nih.gov/10745006/ DOI: 10.1016/s0969-2126(00)00105-2","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"tissue_or_cell_type","value_text":"Recombinant E1b crystal","comparator":null,"unit":null,"notes":"","entity":null}],"evidence":[{"id":"1e9f8c07-6b3c-5804-93d1-03d3d397e5ef","evidence_kind":"source_excerpt","locator":"Lines 650-660","start_line":650,"end_line":660,"excerpt":"### mg-bckdh-potassium-site\nHuman E1b contains potassium sites, including one organizing a loop near the ThDP cofactor.\nCondition category: normal\nnutrient_topic: Magnesium research collection; topical membership is not evidence of a direct dietary effect.\nplain_language: Potassium also helps shape this B1-dependent enzyme; the metal roles are distinct.\norganism: Homo sapiens\ntissue_or_cell_type: Recombinant E1b crystal\nexperimental_model: Human E1b crystallography, deposited structure 1DTW.\nlimitations: A structural potassium site is not a potassium-intake response experiment.\ncross_nutrient: Potassium and magnesium contribute distinct sites in a thiamine-dependent branched-chain ketoacid enzyme.\n[aevarsson-2000-bckdh] Crystal structure of human branched-chain alpha-ketoacid dehydrogenase and the molecular basis of multienzyme complex deficiency in maple syrup urine disease (2000). https://pubmed.ncbi.nlm.nih.gov/10745006/ DOI: 10.1016/s0969-2126(00)00105-2","model_system":"Human E1b crystallography, deposited structure 1DTW.","directness":"author_interpretation","verification_status":"source_derived_draft","notes":"Exact curation-document quotation, not publisher quotation. Study references: [aevarsson-2000-bckdh] Crystal structure of human branched-chain alpha-ketoacid dehydrogenase and the molecular basis of multienzyme complex deficiency in maple syrup urine disease (2000). https://pubmed.ncbi.nlm.nih.gov/10745006/ DOI: 10.1016/s0969-2126(00)00105-2","relationship":"supports","weight":1.0,"link_notes":"","source":{"id":"dd101e28-1a2e-5a48-9d1e-809c77514866","stable_key":"import-0f17db03-207f-5910-ac8e-13dfc2f378ce","title":"Magnesium: cross-nutrient mechanisms and deficiency (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":"e111c412f57143a17e8e65e74e8f7888b5bb9a61099873f4767f527fac19bb07","revision_id":"6b7f04f2-66ed-5859-955f-c2b50d4bf041","review_status":"unverified_draft","notes":""}}],"relations":[],"conflicts":[],"corrections":[],"research":null}