Abstract

Active transport of substrates across cytoplasmic membranes is of great physiological, medical and pharmaceutical importance. The glycerol-3-phosphate (G3P) transporter (GlpT) of the E. coli inner membrane is a secondary active antiporter from the ubiquitous major facilitator superfamily that couples the import of G3P? to the efflux of inorganic phosphate (Pi) down its concentration gradient. Integrating information from a novel combination of structural, molecular dynamics simulations and biochemical studies, we identify the residues involved directly in binding of substrate to the inward-facing conformation of GlpT, thus defining the structural basis for the substrate-specificity of this transporter. The substrate binding mechanism involves protonation of a histidine residue at the binding site. Furthermore, our data suggest that the formation and breaking of inter- and intradomain salt bridges control the conformational change of the transporter that accompanies substrate translocation across the membrane. The mechanism we propose may be a paradigm for organophosphate:phosphate antiporters. (c) 2008 Elsevier Ltd. All rights reserved.

Keywords

antiporter; membrane transport; major facilitator superfamily; molecular dynamics simulations; secondary active transport

Published in

Journal of Molecular Biology
2008, Volume: 378, number: 4, pages: 828-839
Publisher: ACADEMIC PRESS LTD ELSEVIER SCIENCE LTD

SLU Authors

• Huang Almqvist, Yafei

  • Department of Molecular Biology, Swedish University of Agricultural Sciences
    

UKÄ Subject classification

Biochemistry and Molecular Biology


Publication identifier

DOI: https://doi.org/10.1016/j.jmb.2008.03.029

Permanent link to this page (URI)

https://res.slu.se/id/publ/17888