Campus Units

Biochemistry, Biophysics and Molecular Biology, Physics and Astronomy

Document Type

Article

Publication Version

Published Version

Publication Date

2006

Journal or Book Title

Journal of Bacteriology

Volume

188

Issue

20

First Page

7290

Last Page

7296

DOI

10.1128/JB.00684-06 7296

Abstract

We previously reported the X-ray structures of wild-type Escherichia coli AcrB, a proton motive force-dependent multidrug efflux pump, and its N109A mutant. These structures presumably reflect the resting state of AcrB, which can bind drugs. After ligand binding, a proton may bind to an acidic residue(s) in the transmembrane domain, i.e., Asp407 or Asp408, within the putative network of electrostatically interacting residues, which also include Lys940 and Thr978, and this may initiate a series of conformational changes that result in drug expulsion. Herein we report the X-ray structures of four AcrB mutants, the D407A, D408A, K940A, and T978A mutants, in which the structure of this tight electrostatic network is expected to become disrupted. These mutant proteins revealed remarkably similar conformations, which show striking differences from the previously known conformations of the wild-type protein. For example, the loop containing Phe386 and Phe388, which play a major role in the initial binding of substrates in the central cavity, becomes prominently extended into the center of the cavity, such that binding of large substrate molecules may become difficult. We believe that this new conformation may mimic, at least partially, one of the transient conformations of the transporter during the transport cycle.

Comments

This article is from Journal of Bacteriology 188 (2006): 7290, doi:10.1128/JB.00684-06 7296. Posted with permission.

Copyright Owner

American Society for Microbiology

Language

en

File Format

application/pdf

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