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

FEBS Letters

Schuldiner, Shimon¹  Yerushalmi, Hagit¹ 

[1] Alexander Silberman Institute of Life Sciences, Hebrew University of Jerusalem, 91904 Jerusalem, Israel

关键词: Ion-coupled transporter;    Carboxylic residue;    Substrate binding pocket;    Proton translocation;    Coupling;    EmrE;    TM;    transmembrane segment;    TPP+;    tetraphenylphosphonium;    DCCD;    dicyclohexylcarbodiimide;    EDAC;    1-ethyl-3-(3-dimethylaminopropyl)carbodiimide;    The mutants are named as follows: single amino acid replacements are named with the letter of the original amino acid;    then its position in the protein and the letter of the new amino acid. The mutant in which two carboxyl residues are replaced with Cys is named E25C-D84C;   

DOI  :  10.1016/S0014-5793(00)01677-X

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

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.

【 授权许可】

Unknown