Molecular view of ER membrane remodeling by the Sec61/TRAP translocon
(2023) In EMBO Reports 24(12).- Abstract
Protein translocation across the endoplasmic reticulum (ER) membrane is an essential step during protein entry into the secretory pathway. The conserved Sec61 protein-conducting channel facilitates polypeptide translocation and coordinates cotranslational polypeptide-processing events. In cells, the majority of Sec61 is stably associated with a heterotetrameric membrane protein complex, the translocon-associated protein complex (TRAP), yet the mechanism by which TRAP assists in polypeptide translocation remains unknown. Here, we present the structure of the core Sec61/TRAP complex bound to a mammalian ribosome by cryogenic electron microscopy (cryo-EM). Ribosome interactions anchor the Sec61/TRAP complex in a conformation that renders... (More)
Protein translocation across the endoplasmic reticulum (ER) membrane is an essential step during protein entry into the secretory pathway. The conserved Sec61 protein-conducting channel facilitates polypeptide translocation and coordinates cotranslational polypeptide-processing events. In cells, the majority of Sec61 is stably associated with a heterotetrameric membrane protein complex, the translocon-associated protein complex (TRAP), yet the mechanism by which TRAP assists in polypeptide translocation remains unknown. Here, we present the structure of the core Sec61/TRAP complex bound to a mammalian ribosome by cryogenic electron microscopy (cryo-EM). Ribosome interactions anchor the Sec61/TRAP complex in a conformation that renders the ER membrane locally thinner by significantly curving its lumenal leaflet. We propose that TRAP stabilizes the ribosome exit tunnel to assist nascent polypeptide insertion through Sec61 and provides a ratcheting mechanism into the ER lumen mediated by direct polypeptide interactions.
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- author
- Karki, Sudeep ; Javanainen, Matti ; Rehan, Shahid ; Tranter, Dale ; Kellosalo, Juho ; Huiskonen, Juha ; Happonen, Lotta LU and Paavilainen, Ville
- organization
- publishing date
- 2023
- type
- Contribution to journal
- publication status
- published
- subject
- keywords
- cryo-EM, membrane proteins, protein translocation, secretory proteins, structural biology
- in
- EMBO Reports
- volume
- 24
- issue
- 12
- publisher
- Nature Publishing Group
- external identifiers
-
- pmid:37983950
- scopus:85177189274
- ISSN
- 1469-221X
- DOI
- 10.15252/embr.202357910
- language
- English
- LU publication?
- yes
- additional info
- Funding Information: Research was supported by funding: VOP from the Academy of Finland (338836 and 314672), the Sigrid Juselius Foundation, and the Jane and Aatos Erkko Foundation. JTH from the Academy of Finland (314669). MJ from the Academy of Finland (338160). We are thankful to Pasi Laurinmaki and Benita Löflund (Cryo‐EM unit, Institute of Biotechnology, University of Helsinki) and Zane Dekere for the technical support. We thank members of Professor Timo Otonkoski's group for advice and help in carrying out the insulin secretion assays. We thank Jason van Rooyen (Beamline scientist, Diamond Light Source, UK) for the data collection. Support from the Swedish National Infrastructure for Biological Mass Spectrometry (BioMS) and the SciLifeLab, Integrated Structural Biology (ISB) platform, is gratefully acknowledged. We thank CSC–IT Center for Science for computational resources. We thank Professor Ramanujan Hegde (MRC Laboratory of Molecular Biology, Cambridge, UK) for the kind gift of anti‐TRAPα antibody and Professor Peter Arvan (University of Michigan Medical School, Ann Arbor, MI, USA) for the kind gift of INS‐1 832/13 cells. We thank Prof. Thomas Bell, Dr. Sarah O'Keefe, and Dr. Fabio Lolicato for constructive feedback on the manuscript. Publisher Copyright: © 2023 The Authors. Published under the terms of the CC BY 4.0 license.
- id
- 61196607-b460-4006-9a95-06af561bc233
- date added to LUP
- 2023-11-28 10:24:44
- date last changed
- 2024-04-25 14:07:23
@article{61196607-b460-4006-9a95-06af561bc233,
abstract = {{<p>Protein translocation across the endoplasmic reticulum (ER) membrane is an essential step during protein entry into the secretory pathway. The conserved Sec61 protein-conducting channel facilitates polypeptide translocation and coordinates cotranslational polypeptide-processing events. In cells, the majority of Sec61 is stably associated with a heterotetrameric membrane protein complex, the translocon-associated protein complex (TRAP), yet the mechanism by which TRAP assists in polypeptide translocation remains unknown. Here, we present the structure of the core Sec61/TRAP complex bound to a mammalian ribosome by cryogenic electron microscopy (cryo-EM). Ribosome interactions anchor the Sec61/TRAP complex in a conformation that renders the ER membrane locally thinner by significantly curving its lumenal leaflet. We propose that TRAP stabilizes the ribosome exit tunnel to assist nascent polypeptide insertion through Sec61 and provides a ratcheting mechanism into the ER lumen mediated by direct polypeptide interactions.</p>}},
author = {{Karki, Sudeep and Javanainen, Matti and Rehan, Shahid and Tranter, Dale and Kellosalo, Juho and Huiskonen, Juha and Happonen, Lotta and Paavilainen, Ville}},
issn = {{1469-221X}},
keywords = {{cryo-EM; membrane proteins; protein translocation; secretory proteins; structural biology}},
language = {{eng}},
number = {{12}},
publisher = {{Nature Publishing Group}},
series = {{EMBO Reports}},
title = {{Molecular view of ER membrane remodeling by the Sec61/TRAP translocon}},
url = {{http://dx.doi.org/10.15252/embr.202357910}},
doi = {{10.15252/embr.202357910}},
volume = {{24}},
year = {{2023}},
}