{"id":"d3dbb6f4-13e5-5a43-ad1f-e2feb02285dd","stable_key":"335be270-ea4a-5c8e-ad04-964fd22a439e:vanadium-tf-binding","predicate":"binds_vacant_iron_sites","statement":"V(V) and V(IV) bound vacant transferrin iron-binding sites in culture medium even with a 20-fold molar excess of albumin, without displacing already-bound Fe(III) under those conditions.","claim_class":"mechanistic","status":"source_derived_draft","evidence_grade":"ungraded","direction":"context_dependent","is_public":true,"mechanism_event_id":"f3454656-74a7-58e0-bdc5-cff5819e8fce","mechanism_event_label":"Vanadium can occupy available metal-binding sites without stripping out all bound iron.","subject":{"id":"bef86a6e-28a0-5df9-9306-3f05991aa159","slug":"vanadate-v","display_name":"Vanadate(V), protonation/speciation dependent","entity_type_key":"chemical_species"},"object":{"id":"ac656bc2-967c-568b-b6d5-58c7ff433c94","slug":"tf","display_name":"Human serum transferrin / TF","entity_type_key":"protein"},"evidence_count":1,"mechanism_event":{"id":"f3454656-74a7-58e0-bdc5-cff5819e8fce","stable_key":"335be270-ea4a-5c8e-ad04-964fd22a439e:vanadium-tf-binding-event","event_type":"observed_relationship","label":"Vanadium can occupy available metal-binding sites without stripping out all bound iron.","description":"V(V) and V(IV) bound vacant transferrin iron-binding sites in culture medium even with a 20-fold molar excess of albumin, without displacing already-bound Fe(III) under those conditions.","status":"provisional","compartment":null,"participants":[{"entity":{"id":"bef86a6e-28a0-5df9-9306-3f05991aa159","slug":"vanadate-v","display_name":"Vanadate(V), protonation/speciation dependent","entity_type_key":"chemical_species"},"role":"subject","stoichiometry":null,"state_label":"","sequence_order":0,"notes":""},{"entity":{"id":"ac656bc2-967c-568b-b6d5-58c7ff433c94","slug":"tf","display_name":"Human serum transferrin / TF","entity_type_key":"protein"},"role":"target","stoichiometry":null,"state_label":"","sequence_order":1,"notes":""},{"entity":{"id":"c5cbad45-22c6-594b-ab6b-71880dab1b24","slug":"vanadium","display_name":"Vanadium","entity_type_key":"nutrient_element"},"role":"context_participant","stoichiometry":null,"state_label":"","sequence_order":2,"notes":""},{"entity":{"id":"656eb223-933b-5a40-b70c-0d77537fe717","slug":"vanadyl-iv","display_name":"Oxovanadium(IV) / vanadyl","entity_type_key":"ion"},"role":"context_participant","stoichiometry":null,"state_label":"","sequence_order":3,"notes":""},{"entity":{"id":"964be7ac-43bd-5f3e-8326-94f0590de67a","slug":"iron-iii","display_name":"Ferric iron","entity_type_key":"ion"},"role":"context_participant","stoichiometry":null,"state_label":"","sequence_order":4,"notes":""},{"entity":{"id":"d74adc7c-c253-5604-99bf-73d5ed0c0701","slug":"human-serum-albumin","display_name":"Human serum albumin","entity_type_key":"protein"},"role":"context_participant","stoichiometry":null,"state_label":"","sequence_order":5,"notes":""},{"entity":{"id":"bf79be92-557a-54b3-8f78-7174ed04675d","slug":"human-vanadium-bound-transferrin","display_name":"Human transferrin bound to vanadium(V/IV)","entity_type_key":"protein_state"},"role":"context_participant","stoichiometry":null,"state_label":"","sequence_order":6,"notes":""}]},"contexts":[{"dimension":"evidence_access","value_text":"Primary abstract","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"experimental_model","value_text":"Human transferrin binding experiments under normoxic conditions.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"limitations","value_text":"Does not establish systemic iron deficiency or competition magnitude at dietary exposures.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"nutrient_topic","value_text":"Vanadium collection; molecular form, preparation, species, exposure and manipulation remain explicit.","comparator":null,"unit":null,"notes":"","entity":{"slug":"vanadium","display_name":"Vanadium","entity_type_key":"nutrient_element"}},{"dimension":"plain_language","value_text":"Vanadium can occupy available metal-binding sites without stripping out all bound iron.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"primary_references","value_text":"Vanadium(V/IV)-Transferrin Binding Disrupts the Transferrin Cycle and Reduces Vanadium Uptake and Antiproliferative Activity in Human Lung Cancer Cells. · 2020 · https://pubmed.ncbi.nlm.nih.gov/32578416/ · DOI 10.1021/acs.inorgchem.0c00926","comparator":null,"unit":null,"notes":"","entity":null}],"evidence":[{"id":"07dde037-3700-55d8-8e55-8294cfef573b","evidence_kind":"source_excerpt","locator":"Lines 190-196","start_line":190,"end_line":196,"excerpt":"## vanadium-tf-binding\nVanadium can occupy available metal-binding sites without stripping out all bound iron.\nV(V) and V(IV) bound vacant transferrin iron-binding sites in culture medium even with a 20-fold molar excess of albumin, without displacing already-bound Fe(III) under those conditions.\nModel: Human transferrin binding experiments under normoxic conditions.\nLimitations: Does not establish systemic iron deficiency or competition magnitude at dietary exposures.\nEvidence access: Primary abstract\nVanadium(V/IV)-Transferrin Binding Disrupts the Transferrin Cycle and Reduces Vanadium Uptake and Antiproliferative Activity in Human Lung Cancer Cells. · 2020 · https://pubmed.ncbi.nlm.nih.gov/32578416/ · DOI 10.1021/acs.inorgchem.0c00926","model_system":"Human transferrin binding experiments under normoxic conditions.","directness":"reported_statement","verification_status":"source_derived_draft","notes":"Original curation paraphrase; evidence access and experimental limitations specified.","relationship":"supports","weight":1.0,"link_notes":"","source":{"id":"e4d5d0ba-529b-540f-96ed-e719d116ccfd","stable_key":"import-335be270-ea4a-5c8e-ad04-964fd22a439e","title":"Vanadium: speciation, phosphate-sensitive enzymes and cross-nutrient mechanisms (2026-09-19)","document_type":"imported_text","citation_label":"AI-assisted research curation; primary references, access levels and experimental limitations individually identified. 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