PMID:10878258
| Citation |
Yerushalmi, H and Schuldiner, S (2000) A common binding site for substrates and protons in EmrE, an ion-coupled multidrug transporter. FEBS Lett. 476:93-7 |
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| 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. |
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| Keywords |
Animals; Antiporters/chemistry; Antiporters/metabolism; Bacterial Proteins/chemistry; Bacterial Proteins/metabolism; Binding Sites; Carrier Proteins/chemistry; Carrier Proteins/metabolism; Escherichia coli/metabolism; Escherichia coli Proteins; Membrane Proteins/chemistry; Membrane Proteins/metabolism; Models, Molecular; Protein Conformation |
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