{"id":"f534d37c-3d99-5595-a35b-40b28faddcbd","stable_key":"7fc92b9e-9cbf-556e-8719-6b5244625250:b12-abs-cd320-holo-binding","predicate":"binds","statement":"Purified human placental receptor and recombinant CD320 extracellular domain bound transcobalamin-cobalamin; high-affinity binding did not require the cytoplasmic domain or membrane orientation.","claim_class":"mechanistic","status":"source_derived_draft","evidence_grade":"ungraded","direction":"positive","is_public":true,"mechanism_event_id":"189bf2c9-592e-5fe3-846a-c91464d114db","mechanism_event_label":"The outside portion of CD320 recognizes B12-loaded transcobalamin.","subject":{"id":"99cb2dd2-433b-5c71-b1bc-5be3fbeaf213","slug":"cd320","display_name":"Human transcobalamin receptor / CD320","entity_type_key":"protein"},"object":{"id":"c0d594d4-1445-57e7-b689-d2fbbb2dc00a","slug":"human-holotranscobalamin","display_name":"Human transcobalamin-cobalamin complex","entity_type_key":"protein_complex"},"evidence_count":1,"mechanism_event":{"id":"189bf2c9-592e-5fe3-846a-c91464d114db","stable_key":"7fc92b9e-9cbf-556e-8719-6b5244625250:b12-abs-cd320-holo-binding-event","event_type":"biochemical_relationship","label":"The outside portion of CD320 recognizes B12-loaded transcobalamin.","description":"Purified human placental receptor and recombinant CD320 extracellular domain bound transcobalamin-cobalamin; high-affinity binding did not require the cytoplasmic domain or membrane orientation.","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":"81bccdbc-ffba-51bb-aa61-bce4b43e4103","slug":"tcn2","display_name":"Human transcobalamin / TCN2","entity_type_key":"protein"},"role":"carrier","stoichiometry":null,"state_label":"","sequence_order":1,"notes":""},{"entity":{"id":"99cb2dd2-433b-5c71-b1bc-5be3fbeaf213","slug":"cd320","display_name":"Human transcobalamin receptor / CD320","entity_type_key":"protein"},"role":"subject","stoichiometry":null,"state_label":"","sequence_order":2,"notes":""},{"entity":{"id":"c0d594d4-1445-57e7-b689-d2fbbb2dc00a","slug":"human-holotranscobalamin","display_name":"Human transcobalamin-cobalamin complex","entity_type_key":"protein_complex"},"role":"target","stoichiometry":null,"state_label":"","sequence_order":3,"notes":""}]},"contexts":[{"dimension":"cross_nutrient","value_text":"false","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"experimental_model","value_text":"Human placental protein purification and recombinant receptor-domain analysis","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"exposure","value_text":"Holo-TC binding to native or recombinant CD320","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"limitations","value_text":"Binding-domain result does not show the cytoplasmic tail is dispensable for endocytosis.","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":"The outside portion of CD320 recognizes B12-loaded transcobalamin.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"primary_references","value_text":"[quadros-2009-cd320] The protein and the gene encoding the receptor for the cellular uptake of transcobalamin-bound cobalamin. (2009). https://pubmed.ncbi.nlm.nih.gov/18779389/ DOI: 10.1182/blood-2008-05-158949","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"tissue_or_cell_type","value_text":"Placental plasma membrane/extracellular receptor domain","comparator":null,"unit":null,"notes":"","entity":null}],"evidence":[{"id":"7f460e7e-97a2-528f-bebd-3a94ebf0ce6b","evidence_kind":"source_excerpt","locator":"Lines 361-372","start_line":361,"end_line":372,"excerpt":"### b12-abs-cd320-holo-binding\nPurified human placental receptor and recombinant CD320 extracellular domain bound transcobalamin-cobalamin; high-affinity binding did not require the cytoplasmic domain or membrane orientation.\nCondition category: normal\nnutrient_topic: Vitamin B12 research collection; topical membership is not evidence of a direct dietary effect.\nplain_language: The outside portion of CD320 recognizes B12-loaded transcobalamin.\norganism: Homo sapiens\ntissue_or_cell_type: Placental plasma membrane/extracellular receptor domain\nexperimental_model: Human placental protein purification and recombinant receptor-domain analysis\nlimitations: Binding-domain result does not show the cytoplasmic tail is dispensable for endocytosis.\nexposure: Holo-TC binding to native or recombinant CD320\ncross_nutrient: false\n[quadros-2009-cd320] The protein and the gene encoding the receptor for the cellular uptake of transcobalamin-bound cobalamin. (2009). https://pubmed.ncbi.nlm.nih.gov/18779389/ DOI: 10.1182/blood-2008-05-158949","model_system":"Human placental protein purification and recombinant receptor-domain analysis","directness":"author_interpretation","verification_status":"source_derived_draft","notes":"Exact curation-document quotation, not publisher quotation. Study references: [quadros-2009-cd320] The protein and the gene encoding the receptor for the cellular uptake of transcobalamin-bound cobalamin. (2009). https://pubmed.ncbi.nlm.nih.gov/18779389/ DOI: 10.1182/blood-2008-05-158949","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. Not publisher full text.","file_path":"","sha256":"ad5b3a51d36e856aa7fdfd1cc23f690b094689bad87d28e1a621a54675a01c92","revision_id":"118bd616-0c13-549f-bfeb-bc439715b89c","review_status":"unverified_draft","notes":""}}],"relations":[],"conflicts":[],"corrections":[],"research":null}