1. Biochemistry and Chemical Biology
  2. Structural Biology and Molecular Biophysics
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Structural insight into toxin secretion by contact dependent growth inhibition transporters

  1. Jeremy Guerin
  2. Istvan Botos
  3. Zijian Zhang
  4. Karl Lundquist
  5. James C Gumbart
  6. Susan K Buchanan  Is a corresponding author
  1. National Institutes of Health, United States
  2. Georgia Institute of Technology, United States
Research Article
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Cite this article as: eLife 2020;9:e58100 doi: 10.7554/eLife.58100

Abstract

Bacterial contact-dependent growth inhibition (CDI) systems use a type Vb secretion mechanism to export large CdiA toxins across the outer membrane by dedicated outer membrane transporters called CdiB. Here we report the first crystal structures of two CdiB transporters from Acinetobacter baumannii and Escherichia coli. CdiB transporters adopt a TpsB fold, containing a 16-stranded transmembrane β-barrel connected to two periplasmic domains. The lumen of the CdiB pore is occluded by an N-terminal α-helix and the conserved extracellular loop 6; these two elements adopt different conformations in the structures. We identified a conserved DxxG motif located on strand β1 that connects loop 6 through different networks of interactions. Structural modifications of DxxG induce rearrangement of extracellular loops and alter interactions with the N-terminal α-helix, preparing the system for α-helix ejection. Using structural biology, functional assays, and molecular dynamics simulations, we show how the barrel pore is primed for CdiA toxin secretion.

Data availability

Diffraction data have been deposited in PDB under the accession code 6WIL and 6WIM.All data generated or analysed during this study are included in the manuscript and supporting files and videos.

Article and author information

Author details

  1. Jeremy Guerin

    Laboratory of Molecular Biology, National Institute of Diabetes & Digestive & Kidney Diseases, National Institutes of Health, Bethesda, United States
    Competing interests
    The authors declare that no competing interests exist.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0003-2622-040X
  2. Istvan Botos

    Laboratory of Molecular Biology, National Institute of Diabetes & Digestive & Kidney Diseases, National Institutes of Health, Bethesda, United States
    Competing interests
    The authors declare that no competing interests exist.
  3. Zijian Zhang

    School of Physics, Georgia Institute of Technology, Atlanta, United States
    Competing interests
    The authors declare that no competing interests exist.
  4. Karl Lundquist

    School of Physics, Georgia Institute of Technology, Atlanta, United States
    Competing interests
    The authors declare that no competing interests exist.
  5. James C Gumbart

    Physics, Georgia Institute of Technology, Atlanta, United States
    Competing interests
    The authors declare that no competing interests exist.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0002-1510-7842
  6. Susan K Buchanan

    Laboratory of Molecular Biology, National Institute of Diabetes & Digestive & Kidney Diseases, National Institutes of Health, Bethesda, United States
    For correspondence
    susan.buchanan2@nih.gov
    Competing interests
    The authors declare that no competing interests exist.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0001-9657-7119

Funding

National Institutes of Health (Intramural Research Program)

  • Jeremy Guerin
  • Istvan Botos
  • Susan K Buchanan

National Science Foundation (MCB-1452464)

  • Zijian Zhang
  • Karl Lundquist
  • James C Gumbart

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

Reviewing Editor

  1. Merritt Maduke, Stanford University School of Medicine, United States

Publication history

  1. Received: April 21, 2020
  2. Accepted: October 21, 2020
  3. Accepted Manuscript published: October 22, 2020 (version 1)
  4. Version of Record published: November 5, 2020 (version 2)

Copyright

This is an open-access article, free of all copyright, and may be freely reproduced, distributed, transmitted, modified, built upon, or otherwise used by anyone for any lawful purpose. The work is made available under the Creative Commons CC0 public domain dedication.

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