A common binding site for substrates and protons in EmrE, an ion‐coupled multidrug transporter
Open Access
- 26 June 2000
- journal article
- review article
- Published by Wiley in FEBS Letters
- Vol. 476 (1-2) , 93-97
- https://doi.org/10.1016/s0014-5793(00)01677-x
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.Keywords
This publication has 40 references indexed in Scilit:
- Acidic Residues Involved in Cation and Substrate Interactions in the Na+/Dicarboxylate Cotransporter, NaDC-1Biochemistry, 1999
- Comparative molecular analysis of Na+/H+ exchangers: a unified model for Na+/H+ antiport?FEBS Letters, 1998
- Charged Residues in Transmembrane Domains II and XI of a Vesicular Monoamine Transporter Form a Charge Pair That Promotes High Affinity Substrate RecognitionPublished by Elsevier ,1997
- Mutation of an Amino Acid Residue Influencing Potassium Coupling in the Glutamate Transporter GLT-1 Induces Obligate ExchangeJournal of Biological Chemistry, 1997
- Modification of the pH Profile and Tetrabenazine Sensitivity of Rat VMAT1 by Replacement of Aspartate 404 with GlutamatePublished by Elsevier ,1996
- Monoclonal Antibody 4B1 Alters the pKa of a Carboxylic Acid at Position 325 (Helix X) of the Lactose Permease of Escherichia coliBiochemistry, 1996
- Essential aspartic acid residues, Asp‐133, Asp‐163 and Asp‐164, in the transmembrane helices of a Na+/H+ antiporter (NhaA) from Escherichia coliFEBS Letters, 1995
- Pathway of Proton Transfer in Bacterial Reaction Centers: Role of Aspartate-L213 in Proton Transfers Associated with Reduction of Quinone to DihydroquinoneBiochemistry, 1994
- Proton translocation mechanism and energetics in the light-driven pump bacteriorhodopsinBiochimica et Biophysica Acta (BBA) - Bioenergetics, 1993
- ABC Transporters: From Microorganisms to ManAnnual Review of Cell Biology, 1992