{"id":"57404730-0200-5007-97c1-dc55aa816564","stable_key":"0f17db03-207f-5910-ac8e-13dfc2f378ce:mg-romk1-outward-current-block","predicate":"blocks-outward-current-through","statement":"Cytoplasmic Mg2+ caused voltage-dependent reduction of ROMK1 outward single-channel current without reducing channel open probability.","claim_class":"mechanistic","status":"source_derived_draft","evidence_grade":"ungraded","direction":"negative","is_public":true,"mechanism_event_id":"73ef1876-932d-5041-ae20-bc5feedfb3e6","mechanism_event_label":"Mg inside the cell can obstruct outward potassium flow through ROMK; this is a conduction effect, not evidence that the channel disappears.","subject":{"id":"bff427ab-35f9-59c2-bb24-fd5953bbaec2","slug":"magnesium-ion","display_name":"Mg2+","entity_type_key":"ion"},"object":{"id":"86dc48e4-b2ea-5a6f-a8a0-19c4b6d57169","slug":"romk1","display_name":"ROMK1 splice isoform","entity_type_key":"protein"},"evidence_count":1,"mechanism_event":{"id":"73ef1876-932d-5041-ae20-bc5feedfb3e6","stable_key":"0f17db03-207f-5910-ac8e-13dfc2f378ce:mg-romk1-outward-current-block-event","event_type":"biochemical_relationship","label":"Mg inside the cell can obstruct outward potassium flow through ROMK; this is a conduction effect, not evidence that the channel disappears.","description":"Cytoplasmic Mg2+ caused voltage-dependent reduction of ROMK1 outward single-channel current without reducing channel open probability.","status":"provisional","compartment":{"slug":"plasma-membrane","display_name":"Plasma membrane"},"participants":[{"entity":{"id":"5dd31e52-f51e-51f3-880e-240abcc0ab1d","slug":"potassium-ion","display_name":"Potassium ion","entity_type_key":"ion"},"role":"transported ion","stoichiometry":null,"state_label":"","sequence_order":0,"notes":""},{"entity":{"id":"86dc48e4-b2ea-5a6f-a8a0-19c4b6d57169","slug":"romk1","display_name":"ROMK1 splice isoform","entity_type_key":"protein"},"role":"tested channel isoform","stoichiometry":null,"state_label":"","sequence_order":1,"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":2,"notes":""}]},"contexts":[{"dimension":"cross_nutrient","value_text":"magnesium -> potassium","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"experimental_model","value_text":"Heterologous channel expression and patch-clamp","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"limitations","value_text":"Excised-patch channel behavior does not quantify whole-body potassium loss in humans.","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":"Xenopus laevis host; mammalian ROMK channel","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"plain_language","value_text":"Mg inside the cell can obstruct outward potassium flow through ROMK; this is a conduction effect, not evidence that the channel disappears.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"primary_references","value_text":"[nichols-1994-romk1] Mg(2+)-dependent inward rectification of ROMK1 potassium channels expressed in Xenopus oocytes (1994). https://pubmed.ncbi.nlm.nih.gov/8057249/ DOI: 10.1113/jphysiol.1994.sp020141","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"tissue_or_cell_type","value_text":"Oocyte membrane","comparator":null,"unit":null,"notes":"","entity":null}],"evidence":[{"id":"3b710d9c-c7b6-5c20-8f7f-589a428a55b8","evidence_kind":"source_excerpt","locator":"Lines 104-114","start_line":104,"end_line":114,"excerpt":"### mg-romk1-outward-current-block\nCytoplasmic Mg2+ caused voltage-dependent reduction of ROMK1 outward single-channel current without reducing channel open probability.\nCondition category: normal\nnutrient_topic: Magnesium research collection; topical membership is not evidence of a direct dietary effect.\nplain_language: Mg inside the cell can obstruct outward potassium flow through ROMK; this is a conduction effect, not evidence that the channel disappears.\norganism: Xenopus laevis host; mammalian ROMK channel\ntissue_or_cell_type: Oocyte membrane\nexperimental_model: Heterologous channel expression and patch-clamp\nlimitations: Excised-patch channel behavior does not quantify whole-body potassium loss in humans.\ncross_nutrient: magnesium -> potassium\n[nichols-1994-romk1] Mg(2+)-dependent inward rectification of ROMK1 potassium channels expressed in Xenopus oocytes (1994). https://pubmed.ncbi.nlm.nih.gov/8057249/ DOI: 10.1113/jphysiol.1994.sp020141","model_system":"Heterologous channel expression and patch-clamp","directness":"author_interpretation","verification_status":"source_derived_draft","notes":"Exact curation-document quotation, not publisher quotation. Study references: [nichols-1994-romk1] Mg(2+)-dependent inward rectification of ROMK1 potassium channels expressed in Xenopus oocytes (1994). https://pubmed.ncbi.nlm.nih.gov/8057249/ DOI: 10.1113/jphysiol.1994.sp020141","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}