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Published May 21, 2021 | Supplemental Material + Submitted + Published
Journal Article Open

Receptor compaction and GTPase rearrangement drive SRP-mediated cotranslational protein translocation into the ER


The conserved signal recognition particle (SRP) cotranslationally delivers ~30% of the proteome to the eukaryotic endoplasmic reticulum (ER). The molecular mechanism by which eukaryotic SRP transitions from cargo recognition in the cytosol to protein translocation at the ER is not understood. Here, structural, biochemical, and single-molecule studies show that this transition requires multiple sequential conformational rearrangements in the targeting complex initiated by guanosine triphosphatase (GTPase)–driven compaction of the SRP receptor (SR). Disruption of these rearrangements, particularly in mutant SRP54G226E linked to severe congenital neutropenia, uncouples the SRP/SR GTPase cycle from protein translocation. Structures of targeting intermediates reveal the molecular basis of early SRP-SR recognition and emphasize the role of eukaryote-specific elements in regulating targeting. Our results provide a molecular model for the structural and functional transitions of SRP throughout the targeting cycle and show that these transitions provide important points for biological regulation that can be perturbed in genetic diseases.

Additional Information

© 2021 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works. Distributed under a Creative Commons Attribution NonCommercial License 4.0 (CC BY-NC). Submitted 10 December 2020; Accepted 1 April 2021; Published 21 May 2021. We thank the members of the Shan and Ban laboratory for comments on the manuscript. We thank A. Scaiola for the support with EM data processing and M. Leibundgut for the support with model building. Cryo-EM data were collected at the Scientific Center for Optical and Electron Microscopy at the ETH Zurich (ScopeM). This work was supported by National Institutes of Health grants GM078024 and R35 GM136321, National Science Foundation grant MCB-1929452, and the Gordon and Betty Moore Foundation grant GBMF2939 to S.S.; by the Swiss National Science Foundation (SNSF) (grant number 310030B_163478) and National Center of Excellence in Research (NCCR) RNA and Disease Program of the SNSF (grant number 51NF40_141735) to N.B.; and by National Institutes of Health grant GM130942 and Dean Willard Chair funds to S.W. We gratefully acknowledge the support of NVIDIA Corporation for the Titan Xp GPU used in this research through a GPU Grant program awarded to A.J. Author contributions: J.H.L., A.J., Y.-H.H.F., N.B., and S.S. designed research. J.H.L., Y.-H.H.F., R.Q., X.S., H.-H.H., X.B., and S.C. performed biochemical experiments and analyzed data. A.J. and S.M. purified RNCs for cryo-EM data collection. A.J., S.M., and D.B. collected EM data. A.J. processed cryo-EM data and built atomic models. J.H.L., R.Q., and S.Y.C. performed μs-ALEX experiments and analyzed data. S.W. provided guidance for μs-ALEX analysis. J.H.L., S.S., A.J., and N.B. wrote the manuscript with input from S.C., H.-H.H., S.Y.C. and S.W. Competing interests: S.W. is a consultant to Bio-Rad. The authors declare that they have no other competing interests. Data and materials availability: All the data and associated procedures are described in the manuscript and/or in Supplementary Materials. Cryo-EM maps and model coordinates are deposited in the EMDB as EMD-12303, EMD-12304, and EMD-12305 and in the PDB as PDB ID 7NFX.

Attached Files

Published - eabg0942.full.pdf

Submitted - 2020.01.07.897827v1.full.pdf

Supplemental Material - abg0942_SM.pdf


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August 20, 2023
October 20, 2023