Journal Article

Transport of lipophilic carboxylates is mediated by transmembrane helix 2 in multidrug transporter AcrB

Tam, Heng-Keat, Oswald, Christine, Pos, Klaas M.

2016

Overview

The deployment of multidrug efflux pumps is a powerful defence mechanism for Gram-negative bacterial cells when exposed to antimicrobial agents. The major multidrug efflux transport system in Escherichia coli , AcrAB–TolC, is a tripartite system using the proton-motive force as an energy source. The polyspecific substrate-binding module AcrB uses various pathways to sequester drugs from the periplasm and outer leaflet of the inner membrane. Here we report the asymmetric AcrB structure in complex with fusidic acid at a resolution of 2.5 Å and mutational analysis of the putative fusidic acid binding site at the transmembrane domain. A groove shaped by the interface between transmembrane helix 1 (TM1) and TM2 specifically binds fusidic acid and other lipophilic carboxylated drugs. We propose that these bound drugs are actively displaced by an upward movement of TM2 towards the AcrB periplasmic porter domain in response to protonation events in the transmembrane domain. The AcrB module of the AcrAB-TolC multidrug efflux pump sequesters drugs from the periplasm and outer leaflet of the inner membrane. Here, Oswald et al . provide evidence that lipophilic carboxylated substrates bind to a groove between transmembrane helices TM1 and TM2, for further transport by an upward movement of TM2.

• Publisher: Nature Publishing Group UK,Nature Publishing Group,Nature Portfolio
• Subject: 14/34 / 38/70 / 631/45/535/1266 / 631/45/612/1237 / 82/80 / 82/83 / Acids / Amino Acid Sequence / Anti-Bacterial Agents - pharmacology / Antimicrobial agents / Bacteria / beta-Lactams - metabolism / Binding Sites / Biological Transport - physiology / Carboxylic Acids - metabolism / Cell division / Cloning, Molecular / Drugs / E coli / Energy sources / Escherichia coli - metabolism / Escherichia coli Proteins - genetics / Escherichia coli Proteins - metabolism / Fusidic Acid - chemistry / Fusidic Acid - metabolism / Gene Expression Regulation, Bacterial - drug effects / Gram-negative bacteria / Humanities and Social Sciences / Models, Molecular / Molecular weight / multidisciplinary / Multidrug Resistance-Associated Proteins - genetics / Multidrug Resistance-Associated Proteins - metabolism / Mutagenesis, Site-Directed / Protein Binding / Protein Conformation / Protein Domains / Protons / Science / Science (multidisciplinary)