In vivo experiments do not support the charge zipper model for Tat translocase assembly

  1. Felicity Alcock  Is a corresponding author
  2. Merel PM Damen
  3. Jesper Levring
  4. Ben C Berks  Is a corresponding author
  1. University of Oxford, United Kingdom

Abstract

The twin-arginine translocase (Tat) transports folded proteins across the bacterial cytoplasmic membrane and the plant thylakoid membrane. The Tat translocation site is formed by substrate-triggered oligomerization of the protein TatA. Walther and co-workers have proposed a structural model for the TatA oligomer in which TatA monomers self-assemble using electrostatic ‘charge zippers’ (Cell (2013) 132:15945). This model was supported by in vitro analysis of the oligomeric state of TatA variants containing charge-inverting substitutions. Here we have used live cell assays of TatA assembly and function in Escherichia coli to re-assess the roles of the charged residues of TatA. Our results do not support the charge zipper model. Instead, we observe that substitutions of charged residues located in the amphipathic helix lock TatA in an assembled state, suggesting that these charged residues play a critical role in the protein translocation step that follows TatA assembly.

Article and author information

Author details

  1. Felicity Alcock

    Department of Biochemistry, University of Oxford, Oxford, United Kingdom
    For correspondence
    felicity.alock@bioch.ox.ac.uk
    Competing interests
    The authors declare that no competing interests exist.
  2. Merel PM Damen

    Department of Biochemistry, University of Oxford, Oxford, United Kingdom
    Competing interests
    The authors declare that no competing interests exist.
  3. Jesper Levring

    Department of Biochemistry, University of Oxford, Oxford, United Kingdom
    Competing interests
    The authors declare that no competing interests exist.
  4. Ben C Berks

    Department of Biochemistry, University of Oxford, Oxford, United Kingdom
    For correspondence
    ben.berks@bioch.ox.ac.uk
    Competing interests
    The authors declare that no competing interests exist.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0001-9685-4067

Funding

Wellcome (Investigator Award 107929/Z/15/Z)

  • Ben C Berks

Biotechnology and Biological Sciences Research Council (BB/L002531/1)

  • Ben C Berks

European Commission (Erasmus Trainee Scheme)

  • Merel PM Damen

Microbiology Society (Harry Smith Vacation Studentship VS15/10)

  • Jesper Levring

The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.

Reviewing Editor

  1. Reid Gilmore, University of Massachusetts Medical School, United States

Publication history

  1. Received: July 3, 2017
  2. Accepted: August 30, 2017
  3. Accepted Manuscript published: August 31, 2017 (version 1)
  4. Version of Record published: September 15, 2017 (version 2)

Copyright

© 2017, Alcock et al.

This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.

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  1. Felicity Alcock
  2. Merel PM Damen
  3. Jesper Levring
  4. Ben C Berks
(2017)
In vivo experiments do not support the charge zipper model for Tat translocase assembly
eLife 6:e30127.
https://doi.org/10.7554/eLife.30127

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