{"id":"e978d2c3-0b76-5081-bc0f-91bc1d628407","stable_key":"6cdb37aa-8998-5ea8-829d-4f995caf98fc:l-carnitine-octn2-structure","predicate":"binds","statement":"Human OCTN2 cryo-EM structures identified a sodium-binding cavity separate from the carnitine site, with allosteric coupling supported by electrophysiology.","claim_class":"mechanistic","status":"source_derived_draft","evidence_grade":"ungraded","direction":"context_dependent","is_public":true,"mechanism_event_id":"c3ef89fd-6176-584d-8401-597257c1fd4b","mechanism_event_label":"Sodium supports transport through a separate coupled binding site.","subject":{"id":"38de8704-84db-5770-ac1d-242cd787e798","slug":"sodium-ion","display_name":"Sodium ion","entity_type_key":"ion"},"object":{"id":"ac46b2f2-5367-5d4f-8521-c0a9db19fbbc","slug":"human-octn2-sodium-binding","display_name":"Human OCTN2 allosteric sodium-binding site","entity_type_key":"cellular_process"},"evidence_count":1,"mechanism_event":{"id":"c3ef89fd-6176-584d-8401-597257c1fd4b","stable_key":"6cdb37aa-8998-5ea8-829d-4f995caf98fc:l-carnitine-octn2-structure-event","event_type":"observed_relationship","label":"Sodium supports transport through a separate coupled binding site.","description":"Human OCTN2 cryo-EM structures identified a sodium-binding cavity separate from the carnitine site, with allosteric coupling supported by electrophysiology.","status":"provisional","compartment":null,"participants":[{"entity":{"id":"38de8704-84db-5770-ac1d-242cd787e798","slug":"sodium-ion","display_name":"Sodium ion","entity_type_key":"ion"},"role":"subject","stoichiometry":null,"state_label":"","sequence_order":0,"notes":""},{"entity":{"id":"ac46b2f2-5367-5d4f-8521-c0a9db19fbbc","slug":"human-octn2-sodium-binding","display_name":"Human OCTN2 allosteric sodium-binding site","entity_type_key":"cellular_process"},"role":"target","stoichiometry":null,"state_label":"","sequence_order":1,"notes":""},{"entity":{"id":"fb9ae9da-e4d3-5557-baac-d8b00e98ba10","slug":"slc22a5","display_name":"Human carnitine transporter OCTN2 / SLC22A5","entity_type_key":"protein"},"role":"context_participant","stoichiometry":null,"state_label":"","sequence_order":2,"notes":""},{"entity":{"id":"6e34c035-9371-578f-b799-fd2a14e9e40f","slug":"l-carnitine","display_name":"L-Carnitine","entity_type_key":"small_molecule"},"role":"context_participant","stoichiometry":null,"state_label":"","sequence_order":3,"notes":""}]},"contexts":[{"dimension":"evidence_access","value_text":"Primary abstract","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"experimental_model","value_text":"Human OCTN2 structures in ligand-free, carnitine/sodium-bound and ipratropium-bound conformations; 2025 primary study.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"limitations","value_text":"Structural coupling does not show that more sodium intake increases transport.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"nutrient_topic","value_text":"L-Carnitine collection; isomer, preparation, species, exposure and manipulation remain explicit.","comparator":null,"unit":null,"notes":"","entity":{"slug":"l-carnitine","display_name":"L-Carnitine","entity_type_key":"small_molecule"}},{"dimension":"plain_language","value_text":"Sodium supports transport through a separate coupled binding site.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"primary_references","value_text":"Structural basis of sodium ion-dependent carnitine transport by OCTN2. · 2025 · https://pubmed.ncbi.nlm.nih.gov/41318751/ · DOI 10.1038/s41467-025-66867-6","comparator":null,"unit":null,"notes":"","entity":null}],"evidence":[{"id":"8bfe1acb-54a6-55e2-8a2f-95a74fe067fc","evidence_kind":"source_excerpt","locator":"Lines 490-496","start_line":490,"end_line":496,"excerpt":"## l-carnitine-octn2-structure\nSodium supports transport through a separate coupled binding site.\nHuman OCTN2 cryo-EM structures identified a sodium-binding cavity separate from the carnitine site, with allosteric coupling supported by electrophysiology.\nModel: Human OCTN2 structures in ligand-free, carnitine/sodium-bound and ipratropium-bound conformations; 2025 primary study.\nLimitations: Structural coupling does not show that more sodium intake increases transport.\nEvidence access: Primary abstract\nStructural basis of sodium ion-dependent carnitine transport by OCTN2. · 2025 · https://pubmed.ncbi.nlm.nih.gov/41318751/ · DOI 10.1038/s41467-025-66867-6","model_system":"Human OCTN2 structures in ligand-free, carnitine/sodium-bound and ipratropium-bound conformations; 2025 primary study.","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":"e2c9c42b-806a-55e2-abde-b0320ea94704","stable_key":"import-6cdb37aa-8998-5ea8-829d-4f995caf98fc","title":"L-Carnitine: synthesis, acyl-group transport, fuel selection and nutrient interactions (2026-09-19)","document_type":"imported_text","citation_label":"AI-assisted research curation; primary-abstract references and experimental limitations individually identified. 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