A common binding site for substrates and protons in EmrE, an ion-coupled multidrug transporter

Hagit Yerushalmi, Shimon Schuldiner*

*Corresponding author for this work

Research output: Contribution to journalShort surveypeer-review

68 Scopus citations

Abstract

EmrE is an Escherichia coli 12-kDa multidrug transporter, which confers resistance to a variety of toxic cations by removing them from the cell interior in exchange with two protons. EmrE has only one membrane-embedded charged residue, Glu-14, that is conserved in more than 50 homologous proteins and it is a simple model system to study the role of carboxylic residues in ion-coupled transporters. We have used mutagenesis and chemical modification to show that Glu-14 is part of the substrate binding site. Its role in proton binding and translocation was shown by a study of the effect of pH on ligand binding, uptake, efflux and exchange reactions. We conclude that Glu-14 is an essential part of a binding site, common to substrates and protons. The occupancy of this site is mutually exclusive and provides the basis of the simplest coupling of two fluxes. Copyright (C) 2000 Federation of European Biochemical Societies.

Original languageEnglish
Pages (from-to)93-97
Number of pages5
JournalFEBS Letters
Volume476
Issue number1-2
DOIs
StatePublished - 30 Jun 2000

Keywords

  • Carboxylic residue
  • Coupling
  • EmrE
  • Ion-coupled transporter
  • Proton translocation
  • Substrate binding pocket

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