{"id":"5a922176-c634-5042-9cb3-393be696ed1b","stable_key":"7fc92b9e-9cbf-556e-8719-6b5244625250:b12-abs-cubn-recognition","predicate":"recognizes","statement":"The 3.3-angstrom human IF-cobalamin/CUB5-8 structure showed two separated cubilin CUB domains engaging the two intrinsic factor domains.","claim_class":"mechanistic","status":"source_derived_draft","evidence_grade":"ungraded","direction":"positive","is_public":true,"mechanism_event_id":"7fcb6fe2-f062-5596-b7e1-31e23276915d","mechanism_event_label":"Cubilin recognizes B12 carried by intrinsic factor.","subject":{"id":"7a3dab53-fbcd-58da-9942-21f1a3ed088d","slug":"cubn","display_name":"Human cubilin / CUBN","entity_type_key":"protein"},"object":{"id":"1e7fbe30-20c5-5229-97de-84ad5c3dde84","slug":"human-if-cobalamin","display_name":"Human intrinsic factor-cobalamin complex","entity_type_key":"protein_complex"},"evidence_count":1,"mechanism_event":{"id":"7fcb6fe2-f062-5596-b7e1-31e23276915d","stable_key":"7fc92b9e-9cbf-556e-8719-6b5244625250:b12-abs-cubn-recognition-event","event_type":"biochemical_relationship","label":"Cubilin recognizes B12 carried by intrinsic factor.","description":"The 3.3-angstrom human IF-cobalamin/CUB5-8 structure showed two separated cubilin CUB domains engaging the two intrinsic factor domains.","status":"provisional","compartment":null,"participants":[{"entity":{"id":"b6d9b937-895d-5e0a-8cc5-0454a0b7d373","slug":"vitamin-b12","display_name":"Vitamin B12 (cobalamins)","entity_type_key":"chemical_species"},"role":"nutrient","stoichiometry":null,"state_label":"","sequence_order":0,"notes":""},{"entity":{"id":"490161eb-b7f8-56b6-82bc-77c8c0bdc1ca","slug":"gif","display_name":"Human gastric intrinsic factor / GIF","entity_type_key":"protein"},"role":"carrier","stoichiometry":null,"state_label":"","sequence_order":1,"notes":""},{"entity":{"id":"e359bc15-e675-5d83-b0fe-1d70814e130b","slug":"calcium-ion","display_name":"Calcium ion","entity_type_key":"ion"},"role":"binding-cofactor","stoichiometry":null,"state_label":"","sequence_order":2,"notes":""},{"entity":{"id":"7a3dab53-fbcd-58da-9942-21f1a3ed088d","slug":"cubn","display_name":"Human cubilin / CUBN","entity_type_key":"protein"},"role":"subject","stoichiometry":null,"state_label":"","sequence_order":3,"notes":""},{"entity":{"id":"1e7fbe30-20c5-5229-97de-84ad5c3dde84","slug":"human-if-cobalamin","display_name":"Human intrinsic factor-cobalamin complex","entity_type_key":"protein_complex"},"role":"target","stoichiometry":null,"state_label":"","sequence_order":4,"notes":""}]},"contexts":[{"dimension":"cross_nutrient","value_text":"true","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"experimental_model","value_text":"Recombinant human proteins; X-ray crystallography, PDB 3KQ4","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"exposure","value_text":"Purified IF-cobalamin plus CUB5-8 fragment","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"limitations","value_text":"Partial receptor crystal structure; recognition does not by itself establish endocytosis kinetics.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"nutrient_topic","value_text":"Vitamin B12 research collection; topical membership is not evidence of a direct dietary effect.","comparator":null,"unit":null,"notes":"","entity":{"slug":"vitamin-b12","display_name":"Vitamin B12 (cobalamins)","entity_type_key":"chemical_species"}},{"dimension":"organism","value_text":"Homo sapiens","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"plain_language","value_text":"Cubilin recognizes B12 carried by intrinsic factor.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"primary_references","value_text":"[andersen-2010-if-cubn] Structural basis for receptor recognition of vitamin-B(12)-intrinsic factor complexes. (2010). https://pubmed.ncbi.nlm.nih.gov/20237569/ DOI: 10.1038/nature08874","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"tissue_or_cell_type","value_text":"Extracellular ileal receptor recognition model","comparator":null,"unit":null,"notes":"","entity":null}],"evidence":[{"id":"8560b0a5-51cf-5d54-af1d-5b21a58f81f2","evidence_kind":"source_excerpt","locator":"Lines 244-255","start_line":244,"end_line":255,"excerpt":"### b12-abs-cubn-recognition\nThe 3.3-angstrom human IF-cobalamin/CUB5-8 structure showed two separated cubilin CUB domains engaging the two intrinsic factor domains.\nCondition category: normal\nnutrient_topic: Vitamin B12 research collection; topical membership is not evidence of a direct dietary effect.\nplain_language: Cubilin recognizes B12 carried by intrinsic factor.\norganism: Homo sapiens\ntissue_or_cell_type: Extracellular ileal receptor recognition model\nexperimental_model: Recombinant human proteins; X-ray crystallography, PDB 3KQ4\nlimitations: Partial receptor crystal structure; recognition does not by itself establish endocytosis kinetics.\nexposure: Purified IF-cobalamin plus CUB5-8 fragment\ncross_nutrient: true\n[andersen-2010-if-cubn] Structural basis for receptor recognition of vitamin-B(12)-intrinsic factor complexes. (2010). https://pubmed.ncbi.nlm.nih.gov/20237569/ DOI: 10.1038/nature08874","model_system":"Recombinant human proteins; X-ray crystallography, PDB 3KQ4","directness":"author_interpretation","verification_status":"source_derived_draft","notes":"Exact curation-document quotation, not publisher quotation. Study references: [andersen-2010-if-cubn] Structural basis for receptor recognition of vitamin-B(12)-intrinsic factor complexes. (2010). https://pubmed.ncbi.nlm.nih.gov/20237569/ DOI: 10.1038/nature08874","relationship":"supports","weight":1.0,"link_notes":"","source":{"id":"73145023-2982-5848-aff2-8d8875d6b9c5","stable_key":"import-7fc92b9e-9cbf-556e-8719-6b5244625250","title":"Vitamin B12: mechanisms, deficiency and nutrient interactions (2026-09-17)","document_type":"imported_text","citation_label":"AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. 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