1. Structural Biology and Molecular Biophysics
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Kinetic mechanism of coupled binding in sodium-aspartate symporter GltPh

  1. SeCheol Oh
  2. Olga Boudker  Is a corresponding author
  1. Weill Cornell Medicine, United States
Research Article
  • Cited 14
  • Views 1,687
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Cite this article as: eLife 2018;7:e37291 doi: 10.7554/eLife.37291


Many secondary active membrane transporters pump substrates against concentration gradients by coupling their uptake to symport of sodium ions. Symport requires the substrate and ions to be always transported together. Cooperative binding of the solutes is a key mechanism contributing to coupled transport in the sodium and aspartate symporter from Pyrococcus horikoshii GltPh. Here, we describe the kinetic mechanism of coupled binding for GltPh in the inward facing state. The first of the three coupled sodium ions, binds weakly and slowly, enabling the protein to accept the rest of the ions and the substrate. The last ion binds tightly, but is in rapid equilibrium with solution. Its release is required for the complex disassembly. Thus, the first ion serves to 'open the door' for the substrate, the last ion 'locks the door' once the substrate is in, and one ion contributes to both events.

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Author details

  1. SeCheol Oh

    Department of Physiology and Biophysics, Weill Cornell Medicine, New York, United States
    Competing interests
    No competing interests declared.
  2. Olga Boudker

    Department of Physiology and Biophysics, Weill Cornell Medicine, New York, United States
    For correspondence
    Competing interests
    Olga Boudker, Reviewing editor, eLife.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0001-6965-0851


Howard Hughes Medical Institute

  • Olga Boudker

National Institute of Neurological Disorders and Stroke (R01NS064357)

  • Olga Boudker

National Institute of Neurological Disorders and Stroke (R37NS085318)

  • Olga Boudker

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

Reviewing Editor

  1. José D Faraldo-Gómez, National Heart, Lung and Blood Institute, National Institutes of Health, United States

Publication history

  1. Received: April 5, 2018
  2. Accepted: September 25, 2018
  3. Accepted Manuscript published: September 26, 2018 (version 1)
  4. Version of Record published: October 8, 2018 (version 2)


© 2018, Oh & Boudker

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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