ABSTRACT How chaperones, insertases and translocases facilitate insertion and folding of complex cytoplasmic proteins into cellular membranes is not fully understood. Here we utilize

single-molecule force spectroscopy to observe YidC, a transmembrane chaperone and insertase, sculpting the folding trajectory of the polytopic α-helical membrane protein lactose permease

(LacY). In the absence of YidC, unfolded LacY inserts individual structural segments into the membrane; however, misfolding dominates the process so that folding cannot be completed. YidC

prevents LacY from misfolding by stabilizing the unfolded state from which LacY inserts structural segments stepwise into the membrane until folding is completed. During stepwise insertion,

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SIMILAR CONTENT BEING VIEWED BY OTHERS MONITORING THE BINDING AND INSERTION OF A SINGLE TRANSMEMBRANE PROTEIN BY AN INSERTASE Article Open access 06 December 2021 STRUCTURAL HETEROGENEITY OF

THE ION AND LIPID CHANNEL TMEM16F Article Open access 02 January 2024 STRUCTURAL AND MOLECULAR MECHANISMS FOR MEMBRANE PROTEIN BIOGENESIS BY THE OXA1 SUPERFAMILY Article 04 March 2021

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ACKNOWLEDGEMENTS We thank R.E. Dalbey (The Ohio State University) for providing plasmid pT7-7 encoding YidC with a His10 tag at the C terminus; R. Newton, J. Thoma, S. Hiller and R.E. Dalbey

for encouraging and constructive comments; and S. Weiser for assistance. This work was supported by the Eidgenössische Technische Hochschule Zürich (to D.J.M.), the Swiss National Science

Foundation (grant 205320_160199 to D.J.M.), the Swiss National Center of Competence in Research “NCCR Molecular Systems Engineering” (to D.J.M.), the European Union Marie Curie Actions

program through the ACRITAS Initial Training Network (FP7-PEOPLE-2012-ITN, project 317348 to D.J.M.), U.S. National Institutes of Health grants DK51131, DK069463 and GM073210 (to H.R.K.),

and U.S. National Science Foundation grant MCB-1129551 (to H.R.K.). AUTHOR INFORMATION AUTHORS AND AFFILIATIONS * Department of Biosystems Science and Engineering, Eidgenössische Technische

Hochschule (ETH) Zurich, Basel, Switzerland Tetiana Serdiuk, Stefania A Mari & Daniel J Müller * Department of Physiology, University of California–Los Angeles, Los Angeles, California,

USA Dhandayuthapani Balasubramaniam, Junichi Sugihara & H Ronald Kaback * Department of Microbiology, Immunology & Molecular Genetics, University of California–Los Angeles, Los

Angeles, California, USA H Ronald Kaback * Molecular Biology Institute, University of California–Los Angeles, Los Angeles, California, USA H Ronald Kaback Authors * Tetiana Serdiuk View

author publications You can also search for this author inPubMed Google Scholar * Dhandayuthapani Balasubramaniam View author publications You can also search for this author inPubMed Google

Scholar * Junichi Sugihara View author publications You can also search for this author inPubMed Google Scholar * Stefania A Mari View author publications You can also search for this

author inPubMed Google Scholar * H Ronald Kaback View author publications You can also search for this author inPubMed Google Scholar * Daniel J Müller View author publications You can also

search for this author inPubMed Google Scholar CONTRIBUTIONS T.S., D.J.M. and H.R.K. designed the experiments. J.S. and D.B. cloned, expressed, purified and reconstituted LacY and YidC. T.S.

performed the SMFS experiments. S.A.M. recorded AFM images. All authors analyzed experimental data and wrote the paper. CORRESPONDING AUTHORS Correspondence to H Ronald Kaback or Daniel J

Müller. ETHICS DECLARATIONS COMPETING INTERESTS The authors declare no competing financial interests. SUPPLEMENTARY INFORMATION SUPPLEMENTARY TEXT AND FIGURES Supplementary Results,

Supplementary Figures 1–10 and Supplementary Tables 1–4. (PDF 1501 kb) RIGHTS AND PERMISSIONS Reprints and permissions ABOUT THIS ARTICLE CITE THIS ARTICLE Serdiuk, T., Balasubramaniam, D.,

Sugihara, J. _et al._ YidC assists the stepwise and stochastic folding of membrane proteins. _Nat Chem Biol_ 12, 911–917 (2016). https://doi.org/10.1038/nchembio.2169 Download citation *

Received: 16 April 2016 * Accepted: 14 June 2016 * Published: 05 September 2016 * Issue Date: November 2016 * DOI: https://doi.org/10.1038/nchembio.2169 SHARE THIS ARTICLE Anyone you share

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