The fast release of sticky protons: kinetics of substrate binding and proton release in a multidrug transporter.

ABSTRACT: EmrE is an Escherichia coli H(+)-coupled multidrug transporter that provides a unique experimental paradigm because of its small size and stability, and because its activity can be studied in detergent solution. In this work, we report a study of the transient kinetics of substrate binding and substrate-induced proton release in EmrE. For this purpose, we measured transient changes in the tryptophan fluorescence upon substrate binding and the rates of substrate-induced proton release. The fluorescence of the essential and fully conserved Trp residue at position 63 is sensitive to the occupancy of the binding site with either protons or substrate. The maximal rate of binding to detergent-solubilized EmrE of TPP(+), a high-affinity substrate, is 2 x 10(7) M(-1).s(-1), a rate typical of diffu

SUBMITTER: Adam Y 

PROVIDER: S-EPMC2084284 | biostudies-literature | 2007 Nov

REPOSITORIES: biostudies-literature