Kinetic mechanism of coupled binding in sodium-aspartate symporter GltPh

Abstract
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Abstract

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 Glt_Ph. Here, we describe the kinetic mechanism of coupled binding for Glt_Ph 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.

Data availability

Diffraction data have been deposited in PDB under the accession code 6CTF

The following data sets were generated

1. Boudker O
2. Oh S
(2018) Crystal structure of GltPh fast mutant - R276S/M395R
6CTF.

https://www.rcsb.org/

Article and author information

Author details

SeCheol Oh

Department of Physiology and Biophysics, Weill Cornell Medicine, New York, United States

Competing interests
No competing interests declared.
Olga Boudker

Department of Physiology and Biophysics, Weill Cornell Medicine, New York, United States

For correspondence
olb2003@med.cornell.edu

Competing interests
Olga Boudker, Reviewing editor, eLife.

"This ORCID iD identifies the author of this article:" 0000-0001-6965-0851

Funding

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.

Copyright

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.