1. Structural Biology and Molecular Biophysics
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A CLC-ec1 mutant reveals global conformational change and suggests a unifying mechanism for the Cl/H+ transport cycle

  1. Tanmay S Chavan
  2. Ricky C Cheng
  3. Tao Jiang
  4. Irimpan I Mathews
  5. Richard A Stein
  6. Antoine Koehl
  7. Hassane S Mchaourab
  8. Emad Tajkhorshid  Is a corresponding author
  9. Merritt Maduke  Is a corresponding author
  1. Stanford University School of Medicine, United States
  2. University of Illinois at Urbana-Champaign, United States
  3. Stanford University, United States
  4. Vanderbilt University, United States
Research Article
  • Cited 3
  • Views 1,433
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Cite this article as: eLife 2020;9:e53479 doi: 10.7554/eLife.53479

Abstract

Among coupled exchangers, CLCs uniquely catalyze the exchange of oppositely charged ions (Cl for H+). Transport-cycle models to describe and explain this unusual mechanism have been proposed based on known CLC structures. While the proposed models harmonize with many experimental findings, gaps and inconsistencies in our understanding have remained. One limitation has been that global conformational change – which occurs in all conventional transporter mechanisms – has not been observed in any high-resolution structure. Here, we describe the 2.6 Å structure of a CLC mutant designed to mimic the fully H+-loaded transporter. This structure reveals a global conformational change to improve accessibility for the Cl substrate from the extracellular side and new conformations for two key glutamate residues. Together with DEER measurements, MD simulations, and functional studies, this new structure `provides evidence for a unified model of H+ /Cl transport that reconciles existing data on all CLC-type proteins.

Article and author information

Author details

  1. Tanmay S Chavan

    Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, United States
    Competing interests
    The authors declare that no competing interests exist.
  2. Ricky C Cheng

    Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, United States
    Competing interests
    The authors declare that no competing interests exist.
  3. Tao Jiang

    NIH Center for Macromolecular Modeling and Bioinformatics, Beckman Institute for Advanced Science and Technology, Department of Biochemistry, Center for Biophysics and Quantitative Biology, University of Illinois at Urbana-Champaign, Urbana, United States
    Competing interests
    The authors declare that no competing interests exist.
  4. Irimpan I Mathews

    Stanford Synchrotron Radiation Lightsource, Stanford University, Menlo Park, United States
    Competing interests
    The authors declare that no competing interests exist.
  5. Richard A Stein

    Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, United States
    Competing interests
    The authors declare that no competing interests exist.
  6. Antoine Koehl

    Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, United States
    Competing interests
    The authors declare that no competing interests exist.
  7. Hassane S Mchaourab

    Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, United States
    Competing interests
    The authors declare that no competing interests exist.
  8. Emad Tajkhorshid

    Department of Biochemistry; Center for Biophysics and Quantitative Biology; 5NIH Center for Macromolecular Modeling and Bioinformatics, Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, United States
    For correspondence
    tajkhors@illinois.edu
    Competing interests
    The authors declare that no competing interests exist.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0001-8434-1010
  9. Merritt Maduke

    Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, United States
    For correspondence
    maduke@stanford.edu
    Competing interests
    The authors declare that no competing interests exist.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0001-7787-306X

Funding

National Institutes of Health (GM113195)

  • Hassane S Mchaourab
  • Emad Tajkhorshid
  • Merritt Maduke

American Heart Association (17POST33670553)

  • Tanmay S Chavan

U.S. Department of Energy (DE-AC02-06CH11357)

  • Antoine Koehl

National Institutes of Health (P41GM103393)

  • Irimpan I Mathews

Blue Waters at National Center for Supercomputing Applications

  • Tao Jiang

Extreme Science and Engineering Discovery Environment (MCA06N060)

  • Emad Tajkhorshid

National Institutes of Health (P41-GM104601)

  • Emad Tajkhorshid

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

Reviewing Editor

  1. Leon D Islas, Universidad Nacional Autónoma de México, Mexico

Publication history

  1. Received: November 9, 2019
  2. Accepted: April 18, 2020
  3. Accepted Manuscript published: April 20, 2020 (version 1)
  4. Version of Record published: May 27, 2020 (version 2)

Copyright

© 2020, Chavan 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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