Article | Published:

The atomic structure of a eukaryotic oligosaccharyltransferase complex

Nature volume 555, pages 328333 (15 March 2018) | Download Citation

Abstract

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.

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Acknowledgements

Cryo-EM images were collected in the David Van Andel Advanced Cryo-Electron Microscopy Suite at Van Andel Research Institute. We thank Y. Harada for advice on yeast genetics and D. Nadziejka for proofreading. This work was partially supported by Van Andel Research Institute (to H.L.) and the US National Institutes of Health (GM111742 to H.L.).

Author information

Affiliations

  1. Center for Epigenetics, Van Andel Research Institute, Grand Rapids, Michigan, USA

    • Lin Bai
    • , Amanda Kovach
    •  & Huilin Li
  2. Advanced Science Research Center at the Graduate Center of the City University of New York, New York, New York, USA

    • Tong Wang
  3. David Van Andel Advanced Cryo-Electron Microscopy Suite, Van Andel Research Institute, Grand Rapids, Michigan, USA

    • Gongpu Zhao

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Contributions

L.B. and H.L. designed the project. L.B. and A.K. purified proteins. L.B., T.W. and G.Z. collected cryo-EM data. L.B. processed data. L.B. and H.L. analysed the data and wrote the manuscript.

Competing interests

The authors declare no competing financial interests.

Corresponding author

Correspondence to Huilin Li.

Reviewer Information Nature thanks S. Withers and the other anonymous reviewer(s) for their contribution to the peer review of this work.

Publisher's note: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

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    Life Sciences Reporting Summary

Videos

  1. 1.

    Cryo-EM 3D density Map of the S. cerevisiae OST Complex

    Surface-rendered cryo-EM 3D map of the OST complex segmented according to the eight individual subunits, which are coloured as in Fig. 1.

  2. 2.

    Atomic Model of the S. cerevisiae OST Complex

    Overall structure of the OST complex shown in cartoon. Individual subunits are coloured as in Fig. 1.

  3. 3.

    Atomic Model of the OST-Sec61 Super-Complex

    Docking the structures of OST and Sec61 (PDB ID: 3JC2) into the cryo-electron tomogram of a mammalian Ribosome-Sec61-OST-TRAP complex (EMD-3069) reveals the interface between OST and Sec61.

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https://doi.org/10.1038/nature25755

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