In Situ Structure of the AcrAB-TolC Efflux Pump at Subnanometer Resolution

Authors

Muyuan Chen
Xiaodong Shi
Zhili Yu
Guizhen Fan
Irina I Serysheva
Matthew L Baker
Ben F Luisi
Steven J Ludtke
Zhao Wang

Publication Date

1-6-2022

Journal

Structure

DOI

10.1016/j.str.2021.08.008

PMID

34506732

PMCID

PMC8741639

PubMedCentral® Posted Date

1-6-2023

PubMedCentral® Full Text Version

Author MSS

Published Open-Access

yes

Keywords

Allosteric Regulation, Bacterial Outer Membrane Proteins, Carrier Proteins, Cryoelectron Microscopy, Electron Microscope Tomography, Escherichia coli, Escherichia coli Proteins, Ligands, Lipoproteins, Membrane Transport Proteins, Models, Molecular, Multidrug Resistance-Associated Proteins, Protein Conformation

Abstract

The tripartite AcrAB-TolC assembly, which spans both the inner and outer membranes in Gram-negative bacteria, is an efflux pump that contributes to multidrug resistance. Here, we present the in situ structure of full-length Escherichia coli AcrAB-TolC determined at 7 Å resolution by electron cryo-tomography. The TolC channel penetrates the outer membrane bilayer through to the outer leaflet and exhibits two different configurations that differ by a 60° rotation relative to the AcrB position in the pump assembly. AcrA protomers interact directly with the inner membrane and with AcrB via an interface located in proximity to the AcrB ligand-binding pocket. Our structural analysis suggests that these AcrA-bridged interactions underlie an allosteric mechanism for transmitting drug-evoked signals from AcrB to the TolC channel within the pump. Our study demonstrates the power of in situ electron cryo-tomography, which permits critical insights into the function of bacterial efflux pumps.

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