{"id":"833c3d59-c4c3-5932-9a39-241387aaa45c","stable_key":"dff9f743-3766-5f20-a71e-d6d2bd5bfb6f:a-vision-magnesium-gcap1","predicate":"enables","statement":"Magnesium-bound GCAP1, rather than metal-free GCAP1, activated RetGC1 under low-calcium assay conditions.","claim_class":"mechanistic","status":"source_derived_draft","evidence_grade":"ungraded","direction":"positive","is_public":true,"mechanism_event_id":"c1b3a267-8b26-5116-8a72-ef8a496a2d82","mechanism_event_label":"Magnesium occupancy lets the calcium sensor stimulate cGMP recovery.","subject":{"id":"bff427ab-35f9-59c2-bb24-fd5953bbaec2","slug":"magnesium-ion","display_name":"Mg2+","entity_type_key":"ion"},"object":{"id":"a638ca6e-bd6a-57d7-aa29-c822b27d4bba","slug":"guca1a","display_name":"GCAP1 / GUCA1A","entity_type_key":"protein"},"evidence_count":1,"mechanism_event":{"id":"c1b3a267-8b26-5116-8a72-ef8a496a2d82","stable_key":"dff9f743-3766-5f20-a71e-d6d2bd5bfb6f:a-vision-magnesium-gcap1-event","event_type":"biochemical_relationship","label":"Magnesium occupancy lets the calcium sensor stimulate cGMP recovery.","description":"Magnesium-bound GCAP1, rather than metal-free GCAP1, activated RetGC1 under low-calcium assay conditions.","status":"provisional","compartment":null,"participants":[{"entity":{"id":"e359bc15-e675-5d83-b0fe-1d70814e130b","slug":"calcium-ion","display_name":"Calcium ion","entity_type_key":"ion"},"role":"competing regulatory ion","stoichiometry":null,"state_label":"","sequence_order":0,"notes":""},{"entity":{"id":"c4c3e3f6-c78d-5fd0-8ed9-4e74ec4d3ddc","slug":"gucy2d","display_name":"Retinal guanylyl cyclase 1 / GUCY2D","entity_type_key":"protein"},"role":"activated cyclase","stoichiometry":null,"state_label":"","sequence_order":1,"notes":""},{"entity":{"id":"6d2f509b-3a5b-5a38-b3e7-b148581edec9","slug":"cgmp","display_name":"Cyclic guanosine monophosphate","entity_type_key":"small_molecule"},"role":"downstream product","stoichiometry":null,"state_label":"","sequence_order":2,"notes":""},{"entity":{"id":"bff427ab-35f9-59c2-bb24-fd5953bbaec2","slug":"magnesium-ion","display_name":"Mg2+","entity_type_key":"ion"},"role":"subject","stoichiometry":null,"state_label":"","sequence_order":3,"notes":""},{"entity":{"id":"a638ca6e-bd6a-57d7-aa29-c822b27d4bba","slug":"guca1a","display_name":"GCAP1 / GUCA1A","entity_type_key":"protein"},"role":"target","stoichiometry":null,"state_label":"","sequence_order":4,"notes":""}]},"contexts":[{"dimension":"cross_nutrient","value_text":"Mg2+ and Ca2+ regulate a sensor in vitamin A-dependent phototransduction recovery.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"experimental_model","value_text":"Purified protein metal-binding and cyclase assays","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"limitations","value_text":"No dietary magnesium deficiency or human night-vision outcome was measured.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"nutrient_topic","value_text":"Vitamin A research collection; topical membership is not evidence of a direct dietary effect.","comparator":null,"unit":null,"notes":"","entity":{"slug":"vitamin-a","display_name":"Vitamin A","entity_type_key":"chemical_species"}},{"dimension":"organism","value_text":"Recombinant protein biochemical system","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"plain_language","value_text":"Magnesium occupancy lets the calcium sensor stimulate cGMP recovery.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"primary_references","value_text":"[peshenko-2006] Ca2+ and Mg2+ binding properties of GCAP-1. Evidence that Mg2+-bound form is the physiological activator of photoreceptor guanylyl cyclase (2006). https://pubmed.ncbi.nlm.nih.gov/16793776/ DOI: 10.1074/jbc.M600257200","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"tissue_or_cell_type","value_text":"Photoreceptor-protein model","comparator":null,"unit":null,"notes":"","entity":null}],"evidence":[{"id":"5eb608ad-b95d-53d4-83ec-72a19d28f37a","evidence_kind":"source_excerpt","locator":"Lines 973-983","start_line":973,"end_line":983,"excerpt":"### a-vision-magnesium-gcap1\nMagnesium-bound GCAP1, rather than metal-free GCAP1, activated RetGC1 under low-calcium assay conditions.\nCondition category: normal\nnutrient_topic: Vitamin A research collection; topical membership is not evidence of a direct dietary effect.\nplain_language: Magnesium occupancy lets the calcium sensor stimulate cGMP recovery.\norganism: Recombinant protein biochemical system\ntissue_or_cell_type: Photoreceptor-protein model\nexperimental_model: Purified protein metal-binding and cyclase assays\nlimitations: No dietary magnesium deficiency or human night-vision outcome was measured.\ncross_nutrient: Mg2+ and Ca2+ regulate a sensor in vitamin A-dependent phototransduction recovery.\n[peshenko-2006] Ca2+ and Mg2+ binding properties of GCAP-1. Evidence that Mg2+-bound form is the physiological activator of photoreceptor guanylyl cyclase (2006). https://pubmed.ncbi.nlm.nih.gov/16793776/ DOI: 10.1074/jbc.M600257200","model_system":"Purified protein metal-binding and cyclase assays","directness":"author_interpretation","verification_status":"source_derived_draft","notes":"Exact curation-document quotation, not publisher quotation. Study references: [peshenko-2006] Ca2+ and Mg2+ binding properties of GCAP-1. Evidence that Mg2+-bound form is the physiological activator of photoreceptor guanylyl cyclase (2006). https://pubmed.ncbi.nlm.nih.gov/16793776/ DOI: 10.1074/jbc.M600257200","relationship":"supports","weight":1.0,"link_notes":"","source":{"id":"0c5474e2-be48-547b-b287-9c07a59c9ff1","stable_key":"import-dff9f743-3766-5f20-a71e-d6d2bd5bfb6f","title":"Vitamin A: forms, mechanisms, deficiency and excess (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":"b217224b262abbd77d6a0c8c9beefff9c022fae4d31e2a5273915d769b9a6546","revision_id":"61008909-871f-575c-b5e2-21542689ea3c","review_status":"unverified_draft","notes":""}}],"relations":[],"conflicts":[],"corrections":[],"research":null}