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Title: Kinetic mechanism of coupled binding in sodium-aspartate symporter GltPh

Journal Article · · eLife
ORCiD logo [1]; ORCiD logo [2]
  1. Cornell Univ., Ithaca, NY (United States). Weill Medical College. Dept. of Physiology & Biophysics
  2. Cornell Univ., Ithaca, NY (United States). Weill Medical College. Dept. of Physiology & Biophysics; Howard Hughes Medical Inst., Chevy Chase, MD (United States)

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.

Research Organization:
Argonne National Laboratory (ANL), Argonne, IL (United States)
Sponsoring Organization:
USDOE Office of Science (SC)
Grant/Contract Number:
AC02-06CH11357
OSTI ID:
1628885
Journal Information:
eLife, Vol. 7; ISSN 2050-084X
Publisher:
eLife Sciences Publications, Ltd.Copyright Statement
Country of Publication:
United States
Language:
English

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Glutamate transporters: a broad review of the most recent archaeal and human structures journal August 2019
Investigation of the allosteric coupling mechanism in a glutamate transporter homolog via unnatural amino acid mutagenesis journal July 2019
Highly coupled transport can be achieved in free-exchange transport models journal December 2019
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Structural ensemble of a glutamate transporter homologue in lipid nanodisc environment journal February 2020

Figures / Tables (6)