{"id":"eeed3584-38d4-5abb-bcec-26b0d972a8ff","stable_key":"f992b796-377d-53bf-a39b-7e5d41dbe194:b5-trans-pantothenate-carboxyl-recognition","predicate":"binds","statement":"In the human SMVT–pantothenate structural model, the substrate carboxyl group interacts with backbone amino groups of Ser81/Ala84 and hydrogen-bonds to Tyr156.","claim_class":"mechanistic","status":"source_derived_draft","evidence_grade":"ungraded","direction":"positive","is_public":true,"mechanism_event_id":"22990cbe-a3c9-590e-8cb5-13cca91966e7","mechanism_event_label":"SMVT anchors the charged end of B5 through specific contacts in its binding pocket.","subject":{"id":"3bd59e38-e6b1-5223-b4de-faa33835f5bc","slug":"slc5a6","display_name":"Human sodium-dependent multivitamin transporter / SLC5A6","entity_type_key":"protein"},"object":{"id":"7bc62072-9517-5563-a3b8-8c5ab64a464b","slug":"pantothenate","display_name":"Pantothenate (vitamin B5)","entity_type_key":"small_molecule"},"evidence_count":1,"mechanism_event":{"id":"22990cbe-a3c9-590e-8cb5-13cca91966e7","stable_key":"f992b796-377d-53bf-a39b-7e5d41dbe194:b5-trans-pantothenate-carboxyl-recognition-event","event_type":"biochemical_relationship","label":"SMVT anchors the charged end of B5 through specific contacts in its binding pocket.","description":"In the human SMVT–pantothenate structural model, the substrate carboxyl group interacts with backbone amino groups of Ser81/Ala84 and hydrogen-bonds to Tyr156.","status":"provisional","compartment":null,"participants":[{"entity":{"id":"37a8e96b-f95b-5ba7-a0bc-8ed3cfaf5fd8","slug":"biotin","display_name":"Biotin","entity_type_key":"small_molecule"},"role":"shared_recognition_substrate","stoichiometry":null,"state_label":"","sequence_order":0,"notes":"Overlapping pocket supports the cross-nutrient interpretation."},{"entity":{"id":"ab091982-3acb-5a87-80fb-85dfe292c1e0","slug":"lipoic-acid","display_name":"Lipoic acid","entity_type_key":"small_molecule"},"role":"shared_recognition_substrate","stoichiometry":null,"state_label":"","sequence_order":1,"notes":""},{"entity":{"id":"3bd59e38-e6b1-5223-b4de-faa33835f5bc","slug":"slc5a6","display_name":"Human sodium-dependent multivitamin transporter / SLC5A6","entity_type_key":"protein"},"role":"subject","stoichiometry":null,"state_label":"","sequence_order":2,"notes":""},{"entity":{"id":"7bc62072-9517-5563-a3b8-8c5ab64a464b","slug":"pantothenate","display_name":"Pantothenate (vitamin B5)","entity_type_key":"small_molecule"},"role":"target","stoichiometry":null,"state_label":"","sequence_order":3,"notes":""}]},"contexts":[{"dimension":"cross_nutrient","value_text":"true","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"experimental_model","value_text":"Cryo-EM of engineered human SMVT with nanobody-assisted alignment; functional uptake assays in HEK293T cells","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"exposure","value_text":"3.7-angstrom cryo-EM pantothenate complex; molecular-dynamics support for the binding model.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"limitations","value_text":"Engineered, purified transporter structure supports a binding mechanism; it does not establish nutritional competition severity in vivo. The structural construct has altered biotin transport kinetics relative to wild type. Atom-level interactions are structural-model interpretations; no specific dietary threshold follows.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"nutrient_topic","value_text":"Pantothenic acid (vitamin B5) research collection; topical membership is not evidence of a direct dietary effect.","comparator":null,"unit":null,"notes":"","entity":{"slug":"pantothenate","display_name":"Pantothenate (vitamin B5)","entity_type_key":"small_molecule"}},{"dimension":"organism","value_text":"Homo sapiens","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"plain_language","value_text":"SMVT anchors the charged end of B5 through specific contacts in its binding pocket.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"primary_references","value_text":"[b5-trans-structure2026] Structural basis for multivitamin recognition and transport by human SMVT. (2026). https://pubmed.ncbi.nlm.nih.gov/42364996/ DOI: 10.1038/s41467-026-74948-3","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"tissue_or_cell_type","value_text":"Purified human SMVT ligand-binding pocket","comparator":null,"unit":null,"notes":"","entity":null}],"evidence":[{"id":"c3fa7218-dbbd-5f0d-92b6-0b0edce0b53a","evidence_kind":"source_excerpt","locator":"Lines 418-429","start_line":418,"end_line":429,"excerpt":"### b5-trans-pantothenate-carboxyl-recognition\nIn the human SMVT–pantothenate structural model, the substrate carboxyl group interacts with backbone amino groups of Ser81/Ala84 and hydrogen-bonds to Tyr156.\nCondition category: normal\nnutrient_topic: Pantothenic acid (vitamin B5) research collection; topical membership is not evidence of a direct dietary effect.\nplain_language: SMVT anchors the charged end of B5 through specific contacts in its binding pocket.\norganism: Homo sapiens\ntissue_or_cell_type: Purified human SMVT ligand-binding pocket\nexperimental_model: Cryo-EM of engineered human SMVT with nanobody-assisted alignment; functional uptake assays in HEK293T cells\nlimitations: Engineered, purified transporter structure supports a binding mechanism; it does not establish nutritional competition severity in vivo. The structural construct has altered biotin transport kinetics relative to wild type. Atom-level interactions are structural-model interpretations; no specific dietary threshold follows.\nexposure: 3.7-angstrom cryo-EM pantothenate complex; molecular-dynamics support for the binding model.\ncross_nutrient: true\n[b5-trans-structure2026] Structural basis for multivitamin recognition and transport by human SMVT. (2026). https://pubmed.ncbi.nlm.nih.gov/42364996/ DOI: 10.1038/s41467-026-74948-3","model_system":"Cryo-EM of engineered human SMVT with nanobody-assisted alignment; functional uptake assays in HEK293T cells","directness":"author_interpretation","verification_status":"source_derived_draft","notes":"Exact curation-document quotation, not publisher quotation. Study references: [b5-trans-structure2026] Structural basis for multivitamin recognition and transport by human SMVT. (2026). https://pubmed.ncbi.nlm.nih.gov/42364996/ DOI: 10.1038/s41467-026-74948-3","relationship":"supports","weight":1.0,"link_notes":"","source":{"id":"0716b500-dd0b-5425-b9d0-d88bc9c09e86","stable_key":"import-f992b796-377d-53bf-a39b-7e5d41dbe194","title":"Pantothenic acid (vitamin B5): coenzyme A, 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":"b5a49f5a2373ca6064c9a4e014e052dad2f6f199a82bb09b26b82b831c36110b","revision_id":"78f3e793-f084-5ee2-8703-b661c4b650bf","review_status":"unverified_draft","notes":""}}],"relations":[],"conflicts":[],"corrections":[],"research":null}