Pseudoatomic Structure of the Tripartite Multidrug Efflux Pump AcrAB-TolC Reveals the Intermeshing Cogwheel-like Interaction between AcrA and TolC

Structure. 2016 Feb 2;24(2):272-6. doi: 10.1016/j.str.2015.12.007. Epub 2016 Jan 14.

Abstract

The resistance-nodulation-division type tripartite pump AcrAB-TolC and its homologs are responsible for multidrug resistance in Gram-negative bacteria by expelling a wide variety of toxic substrates. The three essential components, AcrA, AcrB, and TolC, must function in concert with each respective binding partner within the complex. In this study, we report an 8.2-Å resolution cryo-electron microscopy (cryo-EM) 3D reconstruction of the complex that consists of an AcrAB fusion protein and a chimeric TolC protein. The pseudoatomic structure derived from the cryo-EM reconstruction clearly demonstrates a model only compatible with the adaptor bridging mechanism, wherein the funnel-like AcrA hexamer forms an intermeshing cogwheel-like interaction with the α-barrel tip region of TolC. These observations provide a structural milestone for understanding multidrug resistance in pathogenic Gram-negative bacteria, and may also lead to the design of new antibacterial drugs.

Keywords: Complex structure; Cryo-electron microscopy; Membrane protein; Multidrug efflux pump.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Bacterial Proteins / chemistry
  • Bacterial Proteins / metabolism
  • Carrier Proteins / chemistry*
  • Carrier Proteins / metabolism*
  • Cryoelectron Microscopy
  • Drug Resistance, Multiple, Bacterial
  • Gram-Negative Bacteria / chemistry
  • Gram-Negative Bacteria / metabolism*
  • Models, Molecular
  • Molecular Docking Simulation
  • Protein Multimerization
  • Protein Structure, Secondary

Substances

  • Bacterial Proteins
  • Carrier Proteins