{"id":"51e273e6-1378-597f-bf56-d6e62a1c98de","stable_key":"0f17db03-207f-5910-ac8e-13dfc2f378ce:mg-nka-atp-dominates-mg-binding","predicate":"supports","statement":"Shark-pump kinetic fits assigned E1-ATP Mg affinity mainly to ATP coordination, after accounting for free ATP competition.","claim_class":"mechanistic","status":"source_derived_draft","evidence_grade":"ungraded","direction":"positive","is_public":true,"mechanism_event_id":"5637e2e5-65ab-5fa8-919f-e6b83d2b7c2b","mechanism_event_label":"The ATP-associated magnesium supports phosphorylation; free ATP can compete for that magnesium.","subject":{"id":"24904faf-f4b4-5e5a-a2e6-3549fb7a2a2e","slug":"mg-atp","display_name":"Magnesium-ATP complex","entity_type_key":"chemical_species"},"object":{"id":"d4cb49ff-24b3-5f51-9cb2-c7a4e2c5dd5e","slug":"sodium-potassium-atpase-phosphorylation","display_name":"Sodium-potassium ATPase phosphorylation","entity_type_key":"cellular_process"},"evidence_count":1,"mechanism_event":{"id":"5637e2e5-65ab-5fa8-919f-e6b83d2b7c2b","stable_key":"0f17db03-207f-5910-ac8e-13dfc2f378ce:mg-nka-atp-dominates-mg-binding-event","event_type":"biochemical_relationship","label":"The ATP-associated magnesium supports phosphorylation; free ATP can compete for that magnesium.","description":"Shark-pump kinetic fits assigned E1-ATP Mg affinity mainly to ATP coordination, after accounting for free ATP competition.","status":"provisional","compartment":null,"participants":[{"entity":{"id":"bff427ab-35f9-59c2-bb24-fd5953bbaec2","slug":"magnesium-ion","display_name":"Mg2+","entity_type_key":"ion"},"role":"binding ion","stoichiometry":null,"state_label":"","sequence_order":0,"notes":""},{"entity":{"id":"58b974f1-d389-5bf6-81cd-889c44442c42","slug":"atp","display_name":"ATP","entity_type_key":"small_molecule"},"role":"Mg ligand and competing solution species","stoichiometry":null,"state_label":"","sequence_order":1,"notes":""},{"entity":{"id":"27c3e7bd-c6e1-5344-8130-b231a9da2cfb","slug":"sodium-potassium-atpase","display_name":"Sodium-potassium ATPase complexes","entity_type_key":"protein_family"},"role":"enzyme","stoichiometry":null,"state_label":"","sequence_order":2,"notes":""},{"entity":{"id":"24904faf-f4b4-5e5a-a2e6-3549fb7a2a2e","slug":"mg-atp","display_name":"Magnesium-ATP complex","entity_type_key":"chemical_species"},"role":"subject","stoichiometry":null,"state_label":"","sequence_order":3,"notes":""},{"entity":{"id":"d4cb49ff-24b3-5f51-9cb2-c7a4e2c5dd5e","slug":"sodium-potassium-atpase-phosphorylation","display_name":"Sodium-potassium ATPase phosphorylation","entity_type_key":"cellular_process"},"role":"target","stoichiometry":null,"state_label":"","sequence_order":4,"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":"Shark rectal-gland pump membrane fragments; stopped-flow RH421 fluorescence under Na-rich conditions.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"limitations","value_text":"Conclusion concerns E1-ATP; other pump conformations or Mg sites can behave differently.","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":"Shark","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"plain_language","value_text":"The ATP-associated magnesium supports phosphorylation; free ATP can compete for that magnesium.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"primary_references","value_text":"[pilotelle-2009-nka] Mechanism of Mg2+ binding in the Na+,K+-ATPase (2009). https://pmc.ncbi.nlm.nih.gov/articles/PMC2711396/ DOI: 10.1016/j.bpj.2009.01.042","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"tissue_or_cell_type","value_text":"Rectal-gland enzyme membrane fragments","comparator":null,"unit":null,"notes":"","entity":null}],"evidence":[{"id":"fadccfe1-0f89-5666-b35b-8598e5850f5f","evidence_kind":"source_excerpt","locator":"Lines 795-805","start_line":795,"end_line":805,"excerpt":"### mg-nka-atp-dominates-mg-binding\nShark-pump kinetic fits assigned E1-ATP Mg affinity mainly to ATP coordination, after accounting for free ATP competition.\nCondition category: normal\nnutrient_topic: Magnesium research collection; topical membership is not evidence of a direct dietary effect.\nplain_language: The ATP-associated magnesium supports phosphorylation; free ATP can compete for that magnesium.\norganism: Shark\ntissue_or_cell_type: Rectal-gland enzyme membrane fragments\nexperimental_model: Shark rectal-gland pump membrane fragments; stopped-flow RH421 fluorescence under Na-rich conditions.\nlimitations: Conclusion concerns E1-ATP; other pump conformations or Mg sites can behave differently.\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[pilotelle-2009-nka] Mechanism of Mg2+ binding in the Na+,K+-ATPase (2009). https://pmc.ncbi.nlm.nih.gov/articles/PMC2711396/ DOI: 10.1016/j.bpj.2009.01.042","model_system":"Shark rectal-gland pump membrane fragments; stopped-flow RH421 fluorescence under Na-rich conditions.","directness":"author_interpretation","verification_status":"source_derived_draft","notes":"Exact curation-document quotation, not publisher quotation. Study references: [pilotelle-2009-nka] Mechanism of Mg2+ binding in the Na+,K+-ATPase (2009). https://pmc.ncbi.nlm.nih.gov/articles/PMC2711396/ DOI: 10.1016/j.bpj.2009.01.042","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}