6c26
From Proteopedia
The Cryo-EM structure of a eukaryotic oligosaccharyl transferase complex
Structural highlights
FunctionSTT3_YEAST Catalytic subunit of the N-oligosaccharyl transferase (OST) complex which catalyzes the transfer of a high mannose oligosaccharide to an asparagine residue within an Asn-X-Ser/Thr consensus motif in nascent polypeptide chains. N-glycosylation occurs cotranslationally and the complex associates with the Sec61 complex at the channel-forming translocon complex that mediates protein translocation across the endoplasmic reticulum (ER). All subunits are required for a maximal enzyme activity.[1] Publication Abstract from PubMedN-glycosylation is a ubiquitous modification of eukaryotic secretory and membrane-bound proteins; about 90% of glycoproteins are N-glycosylated. The reaction is catalysed by an eight-protein oligosaccharyltransferase complex, OST, embedded in the ER membrane. Our understanding of eukaryotic protein N-glycosylation has been limited owing to the lack of high-resolution structures. Here we report a 3.5-A resolution cryo-EM structure of the Saccharomyces cerevisiae OST, revealing the structures of Ost1-5, Stt3, Wbp1, and Swp1. We found that seven phospholipids mediate many of the inter-subunit interactions, and an Stt3 N-glycan mediates interactions with Wbp1 and Swp1 in the lumen. Ost3 was found to mediate the OST-Sec61 translocon interface, funnelling the acceptor peptide towards the OST catalytic site as the nascent peptide emerges from the translocon. The structure provides novel insights into co-translational protein N-glycosylation and may facilitate the development of small-molecule inhibitors targeting this process. The atomic structure of a eukaryotic oligosaccharyltransferase complex.,Bai L, Wang T, Zhao G, Kovach A, Li H Nature. 2018 Jan 22. pii: nature25755. doi: 10.1038/nature25755. PMID:29466327[2] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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