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A CLC-ec1 mutant reveals global conformational change and suggests a unifying mechanism for the CLC Cl–/H+ transport cycle

Chavan, Tanmay S, Cheng, Ricky C, Jiang, Tao, Mathews, Irimpan I, Stein, Richard A, Koehl, Antoine, Mchaourab, Hassane S, Tajkhorshid, Emad, Maduke, Merritt·2020·eLife
DOI 10.7554/elife.53479PMC PMC7253180

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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.

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Metadata

Authors
Chavan, T. S., Cheng, R. C., Jiang, T., Mathews, I. I., Stein, R. A., Koehl, A., Mchaourab, H. S., Tajkhorshid, E., & Maduke, M.
Affiliations
  • Department of Molecular & Cellular Physiology, Stanford University School of Medicine, Stanford, United States
  • 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
  • Stanford Synchrotron Radiation Lightsource, Stanford University, Menlo Park, United States
  • Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, United States
ORCID
Venue
eLife
Publisher
eLife Sciences Publications, Ltd
Published
2020-04-20
Volume
9
ISSN
2050-084X
DOI
10.7554/elife.53479
PMC
PMC7253180
Cited by
49
References
0
Language
en
Licence
Funders
  • National Institutes of Health (GM113195, P41GM103393, P41-GM104601)
  • American Heart Association (17POST33670553)
  • U.S. Department of Energy (DE-AC02-06CH11357)
  • University of Illinois at Urbana-Champaign (Blue Waters at National Center for Supercomputing Applications)
  • Extreme Science and Engineering Discovery Environment (MCA06N060)

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