Center for Epigenetics, Van Andel Research Institute, Grand Rapids, Michigan, USA.
Advanced Science Research Center at the Graduate Center of the City University of New York, New York, New York, USA.
Nature. 2018 Mar 15;555(7696):328-333. doi: 10.1038/nature25755. Epub 2018 Jan 22.
N-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 (OST) complex that is embedded in the endoplasmic reticulum 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 Å resolution cryo-electron microscopy structure of the Saccharomyces cerevisiae OST complex, revealing the structures of subunits Ost1-Ost5, 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 insights into co-translational protein N-glycosylation, and may facilitate the development of small-molecule inhibitors that target this process.
N-糖基化是真核分泌蛋白和膜结合蛋白的普遍修饰方式；大约 90%的糖蛋白都发生了 N-糖基化。该反应由嵌入内质网膜中的八蛋白寡糖基转移酶（OST）复合物催化。由于缺乏高分辨率结构，我们对真核蛋白 N-糖基化的理解一直受到限制。在这里，我们报告了酿酒酵母 OST 复合物的 3.5Å 分辨率冷冻电镜结构，揭示了 Ost1-Ost5、Stt3、Wbp1 和 Swp1 亚基的结构。我们发现，有 7 种磷脂介导了许多亚基间的相互作用，而 Stt3 的 N-聚糖与内质网腔中的 Wbp1 和 Swp1 相互作用。发现 Ost3 介导了 OST-Sec61 易位通道的接口，将接受肽引导到 OST 催化位点，因为新生肽从易位通道中出现。该结构提供了对共翻译蛋白 N-糖基化的深入了解，并可能促进针对该过程的小分子抑制剂的开发。
