Welcome to the new version of CaltechAUTHORS. Login is currently restricted to library staff. If you notice any issues, please email coda@library.caltech.edu
Published November 6, 2017 | Published + Supplemental Material
Journal Article Open

SecA mediates cotranslational targeting and translocation of an inner membrane protein


Protein targeting to the bacterial plasma membrane was generally thought to occur via two major pathways: cotranslational targeting by signal recognition particle (SRP) and posttranslational targeting by SecA and SecB. Recently, SecA was found to also bind ribosomes near the nascent polypeptide exit tunnel, but the function of this SecA–ribosome contact remains unclear. In this study, we show that SecA cotranslationally recognizes the nascent chain of an inner membrane protein, RodZ, with high affinity and specificity. In vitro reconstitution and in vivo targeting assays show that SecA is necessary and sufficient to direct the targeting and translocation of RodZ to the bacterial plasma membrane in an obligatorily cotranslational mechanism. Sequence elements upstream and downstream of the RodZ transmembrane domain dictate nascent polypeptide selection by SecA instead of the SRP machinery. These findings identify a new route for the targeting of inner membrane proteins in bacteria and highlight the diversity of targeting pathways that enables an organism to accommodate diverse nascent proteins.

Additional Information

© 2017 Wang et al. This article is distributed under the terms of an Attribution–Noncommercial–Share Alike–No Mirror Sites license for the first six months after the publication date (see http ://www .rupress .org /terms/). After six months it is available under a Creative Commons License (Attribution–Noncommercial–Share Alike 4.0 International license, as described at https ://creativecommons .org /licenses /by -nc-sa /4.0/). Submitted: 5 April 2017; Revision received 17 July 2017; Accepted: 2 August 2017; Published September 19, 2017. We thank Stephen H. White and Eric Lindner for discussions and members of the Shan group for comments on the manuscript. This work was supported by National Institutes of Health grant GM107368A and the Gordon and Betty Moore Foundation through grant GBMF2939 to S.-o. Shan. The authors declare no competing financial interests. Author contributions: S. Wang designed and performed most of the experiments. C.-I Yang assisted in measuring the binding affinity of RNCs to SecA and SRP. S. Wang and S.-o. Shan wrote the paper. S.-o. Shan conceived the project. All authors reviewed the manuscript.

Attached Files

Published - 3639.full.pdf

Supplemental Material - JCB_201704036_TableS1.pdf

Supplemental Material - JCB_201704036_sm.pdf


Files (3.3 MB)
Name Size Download all
1.1 MB Preview Download
2.2 MB Preview Download
45.2 kB Preview Download

Additional details

August 19, 2023
October 17, 2023