{"id":"6cd636ac-238c-5d16-9ffd-03af5756d114","stable_key":"6612c190-1948-5bcf-bbe3-a7f6c50fa3cf:l-proline-sit1-ace2","predicate":"forms_complex_with","statement":"Cryo-EM resolved human SIT1 in complex with ACE2, with pipecolate-bound and substrate-free conformations identifying the cytoplasmic gate and substrate-release changes.","claim_class":"mechanistic","status":"source_derived_draft","evidence_grade":"ungraded","direction":"context_dependent","is_public":true,"mechanism_event_id":"c937260a-955e-59fe-b39e-829cb6cb8bdd","mechanism_event_label":"A transporter can use a partner protein and still have its own distinct transport mechanism.","subject":{"id":"01b4d4c1-f1a8-59e3-84e3-fb851d5ddf46","slug":"slc6a20","display_name":"Human imino-acid transporter / SLC6A20","entity_type_key":"protein"},"object":{"id":"03e663ce-ec53-5c07-b3dc-d002a595bb63","slug":"ace2","display_name":"Human angiotensin-converting enzyme 2 / ACE2","entity_type_key":"protein"},"evidence_count":1,"mechanism_event":{"id":"c937260a-955e-59fe-b39e-829cb6cb8bdd","stable_key":"6612c190-1948-5bcf-bbe3-a7f6c50fa3cf:l-proline-sit1-ace2-event","event_type":"observed_relationship","label":"A transporter can use a partner protein and still have its own distinct transport mechanism.","description":"Cryo-EM resolved human SIT1 in complex with ACE2, with pipecolate-bound and substrate-free conformations identifying the cytoplasmic gate and substrate-release changes.","status":"provisional","compartment":null,"participants":[{"entity":{"id":"01b4d4c1-f1a8-59e3-84e3-fb851d5ddf46","slug":"slc6a20","display_name":"Human imino-acid transporter / SLC6A20","entity_type_key":"protein"},"role":"subject","stoichiometry":null,"state_label":"","sequence_order":0,"notes":""},{"entity":{"id":"03e663ce-ec53-5c07-b3dc-d002a595bb63","slug":"ace2","display_name":"Human angiotensin-converting enzyme 2 / ACE2","entity_type_key":"protein"},"role":"target","stoichiometry":null,"state_label":"","sequence_order":1,"notes":""},{"entity":{"id":"70ccd53c-83ad-5251-a4f5-6370973bc40a","slug":"l-proline","display_name":"L-Proline","entity_type_key":"small_molecule"},"role":"context_participant","stoichiometry":null,"state_label":"","sequence_order":2,"notes":""}]},"contexts":[{"dimension":"evidence_access","value_text":"Primary full text","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"experimental_model","value_text":"Purified human ACE2-SIT1 complex; pipecolate is a proline-related ligand, not proline itself.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"limitations","value_text":"ACE2 partnership does not establish that proline intake changes susceptibility to viral infection.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"nutrient_topic","value_text":"L-Proline collection; species, compartment, exposure, co-substrates and manipulation remain explicit.","comparator":null,"unit":null,"notes":"","entity":{"slug":"l-proline","display_name":"L-Proline","entity_type_key":"small_molecule"}},{"dimension":"plain_language","value_text":"A transporter can use a partner protein and still have its own distinct transport mechanism.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"primary_references","value_text":"Structure and function of the SIT1 proline transporter in complex with the COVID-19 receptor ACE2. · 2024 · https://pubmed.ncbi.nlm.nih.gov/38951531/ · DOI 10.1038/s41467-024-48921-x","comparator":null,"unit":null,"notes":"","entity":null}],"evidence":[{"id":"2f983529-3c5c-5c6a-83e4-5923cdfac012","evidence_kind":"source_excerpt","locator":"Lines 182-188","start_line":182,"end_line":188,"excerpt":"## l-proline-sit1-ace2\nA transporter can use a partner protein and still have its own distinct transport mechanism.\nCryo-EM resolved human SIT1 in complex with ACE2, with pipecolate-bound and substrate-free conformations identifying the cytoplasmic gate and substrate-release changes.\nModel: Purified human ACE2-SIT1 complex; pipecolate is a proline-related ligand, not proline itself.\nLimitations: ACE2 partnership does not establish that proline intake changes susceptibility to viral infection.\nEvidence access: Primary full text\nStructure and function of the SIT1 proline transporter in complex with the COVID-19 receptor ACE2. · 2024 · https://pubmed.ncbi.nlm.nih.gov/38951531/ · DOI 10.1038/s41467-024-48921-x","model_system":"Purified human ACE2-SIT1 complex; pipecolate is a proline-related ligand, not proline itself.","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":"e5aa7fc5-ee52-5376-8169-416082a89fd1","stable_key":"import-6612c190-1948-5bcf-bbe3-a7f6c50fa3cf","title":"L-Proline: synthesis, collagen processing, redox metabolism 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. Not publisher full text.","file_path":"","sha256":"7b7f1981f9c7897fbb6baa19425bdc19dede78ad4d66fa554394b8337c7366fb","revision_id":"4971a925-fa70-59f8-8030-d3029a18a62f","review_status":"unverified_draft","notes":""}}],"relations":[],"conflicts":[],"corrections":[],"research":null}