{"id":"755382c8-0071-54e3-bc6d-982b0fe20e56","stable_key":"research:archaeal-cys-trna","predicate":"catalyzes_formation_of","statement":"Archaeal SepCysS converts tRNA-bound phosphoserine into Cys-tRNA; Sec is therefore not uniquely synthesized on tRNA across all life.","claim_class":"mechanistic","status":"source_derived_draft","evidence_grade":"literature_reviewed:direct_experimental","direction":"positive","is_public":true,"mechanism_event_id":"0c71006b-3207-5baa-a053-d48cb4b71e02","mechanism_event_label":"Some archaea also make cysteine while it is attached to tRNA.","subject":{"id":"7715cf34-e072-51b2-9110-07424d8c1245","slug":"sepcyss","display_name":"SepCysS","entity_type_key":"protein"},"object":{"id":"0147b86c-9151-5e28-94e5-378d7dd21fe9","slug":"cys-trna","display_name":"cysteinyl-tRNA Cys","entity_type_key":"rna"},"evidence_count":1,"mechanism_event":{"id":"0c71006b-3207-5baa-a053-d48cb4b71e02","stable_key":"research:archaeal-cys-trna","event_type":"catalysis","label":"Some archaea also make cysteine while it is attached to tRNA.","description":"Archaeal SepCysS converts tRNA-bound phosphoserine into Cys-tRNA; Sec is therefore not uniquely synthesized on tRNA across all life.","status":"active","compartment":null,"participants":[{"entity":{"id":"7715cf34-e072-51b2-9110-07424d8c1245","slug":"sepcyss","display_name":"SepCysS","entity_type_key":"protein"},"role":"subject","stoichiometry":null,"state_label":"","sequence_order":0,"notes":""},{"entity":{"id":"0147b86c-9151-5e28-94e5-378d7dd21fe9","slug":"cys-trna","display_name":"cysteinyl-tRNA Cys","entity_type_key":"rna"},"role":"object","stoichiometry":null,"state_label":"","sequence_order":1,"notes":""}]},"contexts":[{"dimension":"cell_type","value_text":"Archaeal cells","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"experimental_model","value_text":"Methanocaldococcus jannaschii enzymes and Methanococcus maripaludis genetics","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"limitations","value_text":"This is not a human cysteine biosynthesis pathway.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"organism","value_text":"Methanocaldococcus jannaschii and Methanococcus maripaludis","comparator":null,"unit":null,"notes":"","entity":null}],"evidence":[{"id":"7ce111d6-b6b0-50bb-84b6-e75b7c768546","evidence_kind":"curated_literature_summary","locator":"lines 1166-1176","start_line":1166,"end_line":1176,"excerpt":"## archaeal-cys-trna\n\nSome archaea also make cysteine while it is attached to tRNA.\n\nArchaeal SepCysS converts tRNA-bound phosphoserine into Cys-tRNA; Sec is therefore not uniquely synthesized on tRNA across all life.\n\nOrganism: Methanocaldococcus jannaschii and Methanococcus maripaludis\nCell type: Archaeal cells\nExperimental model: Methanocaldococcus jannaschii enzymes and Methanococcus maripaludis genetics\nLimitations: This is not a human cysteine biosynthesis pathway.\nPrimary reference: [RNA-Dependent Cysteine Biosynthesis in Archaea](https://pubmed.ncbi.nlm.nih.gov/15790858/)","model_system":"Methanocaldococcus jannaschii enzymes and Methanococcus maripaludis genetics","directness":"author_interpretation","verification_status":"secondary_verified","notes":"Curated summary; inspect the linked primary papers for original methods and results.","relationship":"supports","weight":1.0,"link_notes":"","source":{"id":"4f892f13-06ea-5199-a33c-a703f35c80ae","stable_key":"selenium-research-2026-09-17","title":"Selenium: literature corrections and mechanism additions","document_type":"curated_literature_review","citation_label":"Metabolic Ledger literature curation, 17 September 2026; primary papers linked individually","file_path":"","sha256":"0b818b10c1c7120e5caf7f4d4019d7bd025d745692e424f515d3ef903c9ab7f3","revision_id":"80984e03-5f0f-5877-8094-afef7637444e","review_status":"secondary_verified","notes":"Secondary curated summaries of primary experiments, with explicit models and limitations. Not archived primary full text."}}],"relations":[],"conflicts":[],"corrections":[{"id":"f7f70238-a0f3-507b-9165-8a1f8992fbdd","title":"tRNA-bound amino-acid synthesis is not unique to Sec across all biology","kind":"qualification","status":"qualified","why":"Archaeal cysteine synthesis on tRNA is a direct counterexample to only one in biology.","resolution":"Restrict to human biology or remove uniqueness; later source appropriately calls Sec unusual.","created_at":"2026-09-17 07:19:34","record_type":"qualification","display_label":"Source qualification","record_url":"/corrections/f7f70238-a0f3-507b-9165-8a1f8992fbdd","literature_review":{"revision_id":"80984e03-5f0f-5877-8094-afef7637444e","start_line":1518,"end_line":1523,"papers":[{"paper_key":"sauerwald-2005","title":"RNA-Dependent Cysteine Biosynthesis in Archaea","url":"https://pubmed.ncbi.nlm.nih.gov/15790858/","doi":"10.1126/science.1108329","year":2005,"model":"Methanocaldococcus jannaschii enzymes and Methanococcus maripaludis genetics","summary":"Archaeal Cys is synthesized on tRNA through SepRS/SepCysS."}]},"sides":[{"conflict_id":"f7f70238-a0f3-507b-9165-8a1f8992fbdd","ordinal":0,"label":"Original preserved statement","revision_id":"1fa1ebde-141f-5d47-8a4f-ba87ff84a6c6","start_line":9,"end_line":9,"quote":"Selenocysteine (Sec, U) is the **21st amino acid**, and it's the only one in biology that is *synthesized on its own tRNA*. There is no free Sec pool. There is no SecRS synthetase.","claim_id":null,"source_key":"molecular","source_title":"Selenium: the molecular cascade","claim_ids":[]},{"conflict_id":"f7f70238-a0f3-507b-9165-8a1f8992fbdd","ordinal":1,"label":"Original preserved statement","revision_id":"f8f97804-c1fb-56df-9c06-c02e36e2a5b8","start_line":23,"end_line":23,"quote":"Selenocysteine (Sec) is unusual because it is synthesized on its own tRNA rather than existing as a large free amino-acid pool. There is no dedicated Sec-tRNA synthetase. Instead, two biosynthetic branches converge:","claim_id":null,"source_key":"deficiency","source_title":"Selenium deficiency: a mechanism-first reference","claim_ids":[]},{"conflict_id":"f7f70238-a0f3-507b-9165-8a1f8992fbdd","ordinal":2,"label":"Literature correction and experimental limits","revision_id":"80984e03-5f0f-5877-8094-afef7637444e","start_line":1518,"end_line":1523,"quote":"## tRNA-bound amino-acid synthesis is not unique to Sec across all biology\n\nArchaeal cysteine synthesis on tRNA is a direct counterexample to only one in biology.\n\nRestrict to human biology or remove uniqueness; later source appropriately calls Sec unusual.\nPrimary reference: [RNA-Dependent Cysteine Biosynthesis in Archaea](https://pubmed.ncbi.nlm.nih.gov/15790858/)","claim_id":null,"source_key":"selenium-research-2026-09-17","source_title":"Selenium: literature corrections and mechanism additions","claim_ids":[]}]}],"research":{"topic":"Selenium scientific audit","plain_language":"Some archaea also make cysteine while it is attached to tRNA.","evidence_scope":"direct_experimental","papers":[{"key":"sauerwald-2005","title":"RNA-Dependent Cysteine Biosynthesis in Archaea","url":"https://pubmed.ncbi.nlm.nih.gov/15790858/","doi":"10.1126/science.1108329","year":2005,"model":"Methanocaldococcus jannaschii enzymes and Methanococcus maripaludis genetics","summary":"Archaeal Cys is synthesized on tRNA through SepRS/SepCysS."}]}}