{"id":"cebe70b0-74d3-5247-8b7a-c14abcefc58b","stable_key":"0f17db03-207f-5910-ac8e-13dfc2f378ce:mg-nka-atp-binding-order-boundary","predicate":"can-bind-to","statement":"The 1992 best-fit model allowed free ATP or MgATP to bind before productive Mg-dependent phosphorylation.","claim_class":"mechanistic","status":"source_derived_draft","evidence_grade":"ungraded","direction":"neutral","is_public":true,"mechanism_event_id":"cbaa9083-7f1e-52fe-a5d9-4e58949a6379","mechanism_event_label":"A requirement for magnesium does not prove that only a preformed MgATP molecule can bind.","subject":{"id":"58b974f1-d389-5bf6-81cd-889c44442c42","slug":"atp","display_name":"ATP","entity_type_key":"small_molecule"},"object":{"id":"27c3e7bd-c6e1-5344-8130-b231a9da2cfb","slug":"sodium-potassium-atpase","display_name":"Sodium-potassium ATPase complexes","entity_type_key":"protein_family"},"evidence_count":1,"mechanism_event":{"id":"cbaa9083-7f1e-52fe-a5d9-4e58949a6379","stable_key":"0f17db03-207f-5910-ac8e-13dfc2f378ce:mg-nka-atp-binding-order-boundary-event","event_type":"biochemical_relationship","label":"A requirement for magnesium does not prove that only a preformed MgATP molecule can bind.","description":"The 1992 best-fit model allowed free ATP or MgATP to bind before productive Mg-dependent phosphorylation.","status":"provisional","compartment":null,"participants":[{"entity":{"id":"24904faf-f4b4-5e5a-a2e6-3549fb7a2a2e","slug":"mg-atp","display_name":"Magnesium-ATP complex","entity_type_key":"chemical_species"},"role":"alternative substrate","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":"essential catalytic activator","stoichiometry":null,"state_label":"","sequence_order":1,"notes":""},{"entity":{"id":"58b974f1-d389-5bf6-81cd-889c44442c42","slug":"atp","display_name":"ATP","entity_type_key":"small_molecule"},"role":"subject","stoichiometry":null,"state_label":"","sequence_order":2,"notes":""},{"entity":{"id":"27c3e7bd-c6e1-5344-8130-b231a9da2cfb","slug":"sodium-potassium-atpase","display_name":"Sodium-potassium ATPase complexes","entity_type_key":"protein_family"},"role":"target","stoichiometry":null,"state_label":"","sequence_order":3,"notes":""}]},"contexts":[{"dimension":"cross_nutrient","value_text":"Magnesium-dependent ATP chemistry is coupled to sodium and potassium handling by the pump; serum magnesium is not the enzyme-site concentration.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"experimental_model","value_text":"Pig-kidney Na/K-ATPase rapid-mixing phosphorylation; Na-containing, K-free medium; varied ATP and MgCl2.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"limitations","value_text":"Kinetic model, not proof of Mg-free catalysis; binding and phosphate transfer are distinct.","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":"Sus scrofa","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"plain_language","value_text":"A requirement for magnesium does not prove that only a preformed MgATP molecule can bind.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"primary_references","value_text":"[campos-1992-nka] Effects of magnesium and ATP on pre-steady-state phosphorylation kinetics of the Na+,K(+)-ATPase (1992). https://pubmed.ncbi.nlm.nih.gov/1314673/ DOI: 10.1016/0005-2736(92)90161-e","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"tissue_or_cell_type","value_text":"Kidney enzyme","comparator":null,"unit":null,"notes":"","entity":null}],"evidence":[{"id":"c4f6ede8-5722-5ae5-9d6c-4887266613cc","evidence_kind":"source_excerpt","locator":"Lines 783-793","start_line":783,"end_line":793,"excerpt":"### mg-nka-atp-binding-order-boundary\nThe 1992 best-fit model allowed free ATP or MgATP to bind before productive Mg-dependent phosphorylation.\nCondition category: normal\nnutrient_topic: Magnesium research collection; topical membership is not evidence of a direct dietary effect.\nplain_language: A requirement for magnesium does not prove that only a preformed MgATP molecule can bind.\norganism: Sus scrofa\ntissue_or_cell_type: Kidney enzyme\nexperimental_model: Pig-kidney Na/K-ATPase rapid-mixing phosphorylation; Na-containing, K-free medium; varied ATP and MgCl2.\nlimitations: Kinetic model, not proof of Mg-free catalysis; binding and phosphate transfer are distinct.\ncross_nutrient: Magnesium-dependent ATP chemistry is coupled to sodium and potassium handling by the pump; serum magnesium is not the enzyme-site concentration.\n[campos-1992-nka] Effects of magnesium and ATP on pre-steady-state phosphorylation kinetics of the Na+,K(+)-ATPase (1992). https://pubmed.ncbi.nlm.nih.gov/1314673/ DOI: 10.1016/0005-2736(92)90161-e","model_system":"Pig-kidney Na/K-ATPase rapid-mixing phosphorylation; Na-containing, K-free medium; varied ATP and MgCl2.","directness":"author_interpretation","verification_status":"source_derived_draft","notes":"Exact curation-document quotation, not publisher quotation. Study references: [campos-1992-nka] Effects of magnesium and ATP on pre-steady-state phosphorylation kinetics of the Na+,K(+)-ATPase (1992). https://pubmed.ncbi.nlm.nih.gov/1314673/ DOI: 10.1016/0005-2736(92)90161-e","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}