Formation of a β-barrel membrane protein is catalyzed by the interior surface of the assembly machine protein BamA

  1. James Lee
  2. David Tomasek
  3. Thiago Santos
  4. Mary D May
  5. Ina Meuskens
  6. Daniel Kahne  Is a corresponding author
  1. Harvard University, United States

Abstract

The β-barrel assembly machine (Bam) complex in Gram-negative bacteria and its counterparts in mitochondria and chloroplasts fold and insert outer membrane β-barrel proteins. BamA, an essential component of the complex, is itself a β-barrel and is proposed to play a central role in assembling other barrel substrates. Here, we map the path of substrate insertion by the Bam complex using site-specific crosslinking to understand the molecular mechanisms that control β-barrel folding and release. We find that the C-terminal strand of the substrate is stably held by BamA and that the N-terminal strands of the substrate are assembled inside the BamA β-barrel. Importantly, we identify contacts between the assembling β-sheet and the BamA interior surface that determine the rate of substrate folding. Our results support a model in which the interior wall of BamA acts as a chaperone to catalyze β-barrel assembly.

Data availability

All data generated or analyzed during this study are included in the manuscript and supporting files.

Article and author information

Author details

  1. James Lee

    Department of Molecular and Cellular Biology, Harvard University, Cambridge, United States
    Competing interests
    The authors declare that no competing interests exist.
  2. David Tomasek

    Department of Molecular and Cellular Biology, Harvard University, Cambridge, United States
    Competing interests
    The authors declare that no competing interests exist.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0003-1212-4601
  3. Thiago Santos

    Department of Chemistry and Chemical Biology, Harvard University, Cambridge, United States
    Competing interests
    The authors declare that no competing interests exist.
  4. Mary D May

    Department of Chemistry and Chemical Biology, Harvard University, Cambridge, United States
    Competing interests
    The authors declare that no competing interests exist.
  5. Ina Meuskens

    Department of Chemistry and Chemical Biology, Harvard University, Cambridge, United States
    Competing interests
    The authors declare that no competing interests exist.
  6. Daniel Kahne

    Department of Chemistry and Chemical Biology, Harvard University, Cambridge, United States
    For correspondence
    kahne@chemistry.harvard.edu
    Competing interests
    The authors declare that no competing interests exist.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0002-8296-1424

Funding

National Institute of Allergy and Infectious Diseases (AI081059)

  • James Lee
  • David Tomasek
  • Thiago Santos
  • Mary D May
  • Ina Meuskens
  • Daniel Kahne

National Institute of General Medical Sciences (F31GM116210)

  • James Lee

National Institute of Allergy and Infectious Diseases (T32AI132120)

  • Mary D May

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

Reviewing Editor

  1. Ramanujan S Hegde, MRC Laboratory of Molecular Biology, United Kingdom

Publication history

  1. Received: June 29, 2019
  2. Accepted: November 13, 2019
  3. Accepted Manuscript published: November 14, 2019 (version 1)
  4. Version of Record published: December 2, 2019 (version 2)

Copyright

© 2019, Lee 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. James Lee
  2. David Tomasek
  3. Thiago Santos
  4. Mary D May
  5. Ina Meuskens
  6. Daniel Kahne
(2019)
Formation of a β-barrel membrane protein is catalyzed by the interior surface of the assembly machine protein BamA
eLife 8:e49787.
https://doi.org/10.7554/eLife.49787
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