{"id":"10a15c4b-6819-5c4d-86ca-b835a05de282","stable_key":"649e861b-265a-5912-bc36-3a73e53ef892:l-serine-sfxn1-import","predicate":"transports","statement":"Purified SFXN1 transported serine in vitro, and human-cell genetic experiments identified it as an inner-mitochondrial-membrane serine transporter.","claim_class":"mechanistic","status":"source_derived_draft","evidence_grade":"ungraded","direction":"context_dependent","is_public":true,"mechanism_event_id":"25c80073-5e0e-5426-aeef-78451d3447c3","mechanism_event_label":"Serine must cross a compartment boundary before mitochondrial enzymes can use it.","subject":{"id":"8d8fb144-4bb5-5b97-8a22-207c2e9c5206","slug":"sfxn1","display_name":"Human sideroflexin 1 / SFXN1","entity_type_key":"protein"},"object":{"id":"c882cd0b-9d83-5b07-bd1c-fe4d45657dcb","slug":"l-serine","display_name":"L-Serine","entity_type_key":"small_molecule"},"evidence_count":1,"mechanism_event":{"id":"25c80073-5e0e-5426-aeef-78451d3447c3","stable_key":"649e861b-265a-5912-bc36-3a73e53ef892:l-serine-sfxn1-import-event","event_type":"observed_relationship","label":"Serine must cross a compartment boundary before mitochondrial enzymes can use it.","description":"Purified SFXN1 transported serine in vitro, and human-cell genetic experiments identified it as an inner-mitochondrial-membrane serine transporter.","status":"provisional","compartment":null,"participants":[{"entity":{"id":"8d8fb144-4bb5-5b97-8a22-207c2e9c5206","slug":"sfxn1","display_name":"Human sideroflexin 1 / SFXN1","entity_type_key":"protein"},"role":"subject","stoichiometry":null,"state_label":"","sequence_order":0,"notes":""},{"entity":{"id":"c882cd0b-9d83-5b07-bd1c-fe4d45657dcb","slug":"l-serine","display_name":"L-Serine","entity_type_key":"small_molecule"},"role":"target","stoichiometry":null,"state_label":"","sequence_order":1,"notes":""}]},"contexts":[{"dimension":"evidence_access","value_text":"Primary abstract","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"experimental_model","value_text":"Human CRISPR screens, localization and purified-protein transport experiments.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"limitations","value_text":"This does not imply SFXN1 is the only transporter or that all cellular serine is mitochondrial.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"nutrient_topic","value_text":"L-Serine collection; species, compartment, exposure, co-substrates and manipulation remain explicit.","comparator":null,"unit":null,"notes":"","entity":{"slug":"l-serine","display_name":"L-Serine","entity_type_key":"small_molecule"}},{"dimension":"plain_language","value_text":"Serine must cross a compartment boundary before mitochondrial enzymes can use it.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"primary_references","value_text":"SFXN1 is a mitochondrial serine transporter required for one-carbon metabolism. · 2018 · https://pubmed.ncbi.nlm.nih.gov/30442778/ · DOI 10.1126/science.aat9528","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"transport_effect","value_text":"raises","comparator":null,"unit":null,"notes":"Identified as an inner-mitochondrial-membrane serine importer.","entity":null},{"dimension":"transport_pool","value_text":"the mitochondrial matrix","comparator":null,"unit":null,"notes":"Identified as an inner-mitochondrial-membrane serine importer.","entity":null}],"evidence":[{"id":"393446de-4dc4-5831-9b80-32f77c514c69","evidence_kind":"source_excerpt","locator":"Lines 142-148","start_line":142,"end_line":148,"excerpt":"## l-serine-sfxn1-import\nSerine must cross a compartment boundary before mitochondrial enzymes can use it.\nPurified SFXN1 transported serine in vitro, and human-cell genetic experiments identified it as an inner-mitochondrial-membrane serine transporter.\nModel: Human CRISPR screens, localization and purified-protein transport experiments.\nLimitations: This does not imply SFXN1 is the only transporter or that all cellular serine is mitochondrial.\nEvidence access: Primary abstract\nSFXN1 is a mitochondrial serine transporter required for one-carbon metabolism. · 2018 · https://pubmed.ncbi.nlm.nih.gov/30442778/ · DOI 10.1126/science.aat9528","model_system":"Human CRISPR screens, localization and purified-protein transport experiments.","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":"70bcf57a-36bb-563f-9073-2d616e5f155a","stable_key":"import-649e861b-265a-5912-bc36-3a73e53ef892","title":"L-Serine: synthesis, one-carbon metabolism, lipids 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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