{"doi":"10.1101/2025.08.11.669745","title":"The cysteine-rich domain of SEP15, a selenoprotein co-chaperone of the ER chaperone, UDP-glucose:glycoprotein glucosyltransferase, adopts a novel fold","abstract":"Proteins targeted to the secretory pathway are involved in a myriad of biological processes but can only do so when properly folded. Within the endoplasmic reticulum, glycoprotein folding is regulated by the enzyme UDP-glucose:glycoprotein glucosyltransferase (UGGT) and its oxidoreductase partner, the 15-kDa selenoprotein (SEP15 aka SELENOF). The interaction between these two chaperones is poorly understood, limiting understanding of their function. SEP15 is comprised of two domains, a C-terminal thioredoxin-like domain, the structure of which has been reported (PDB 2A4H), and an approximately 50-residue long N-terminal cysteine-rich domain (CRD), of unknown structure. Here, we use a combination of AlphaFold structural predictions and NMR spectroscopy to elucidate the structure of the SEP15 CRD, which mediates the interaction with UGGT. These data reveal that this domain forms a previously undescribed helical fold stabilized by three disulfide bonds between residues C10-C42, C21-C43, and C24-C39. Furthermore, our results validate our reported model of the UGGT/SEP15 complex and lay the foundation for future studies of its interaction with glycoprotein substrates.","journal":"bioRxiv (Cold Spring Harbor Laboratory)","year":2025,"id":572289,"datarank":0.0,"base_score":0.0,"endowment":0.0,"self_citation_contribution":0.0,"citation_network_contribution":0.0,"self_endowment_contribution":0.0,"citer_contribution":0.0,"corpus_percentile":null,"corpus_rank":null,"citation_count":0,"citer_count":0,"citers_with_citation_signal":0,"citers_with_endowment":0,"datacite_reuse_total":0,"is_dataset":false,"is_dataset_confidence":0.9589,"is_data_producer":false,"deposit_databanks":null,"is_oa":true,"file_count":0,"downloads":0,"has_version_chain":false,"published_date":"2025-01-01","fair_score":null,"fair_percentile":null,"algorithm_id":"datarank_citation_only_1hop_v6","ranking_scope":"data_only","authors":[{"id":320511,"name":"Kevin P. Guay","orcid":"0000-0002-3468-942X","position":1,"is_corresponding":false},{"id":1478932,"name":"Owen Hurlbut Lesk","orcid":null,"position":2,"is_corresponding":false},{"id":320512,"name":"Daniel N. Hebert","orcid":"0000-0003-1537-4446","position":3,"is_corresponding":false},{"id":612912,"name":"Lila M. Gierasch","orcid":"0000-0002-5706-115X","position":4,"is_corresponding":false},{"id":410047,"name":"Robert V. Williams","orcid":"0000-0003-1839-6122","position":0,"is_corresponding":true}],"reference_count":25,"raw_metadata":{"citation_network_status":"fetched"},"created_at":"2026-07-19T02:57:23.653298Z","pmid":"40832263","pmcid":null,"fwci":null,"citation_percentile":null,"influential_citations":0,"oa_status":null,"license":null,"views":0,"total_file_size_bytes":0,"version_count":0,"fair_f":null,"fair_a":null,"fair_i":null,"fair_r":null,"fair_zscore":null,"fair_rationale":null,"fair_model":null,"fair_agent_version":null,"fair_fulltext_source":null,"fair_has_llm":null,"fair_computed_at":null,"clinical_trials":[],"software_tools":[],"db_accessions":[],"linked_datasets":[],"topics":[]}