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Tikhonova, EB and Zgurskaya, HI (2004) AcrA, AcrB, and TolC of Escherichia coli Form a Stable Intermembrane Multidrug Efflux Complex. J. Biol. Chem. 279:32116-24

Many transporters of Gram-negative bacteria involved in the extracellular secretion of proteins and the efflux of toxic molecules operate by forming intermembrane complexes. These complexes are proposed to span both inner and outer membranes and create a bridge across the periplasm. In this study, we analyzed interactions between the inner and outer membrane components of the tri-partite multidrug efflux pump AcrAB-TolC from Escherichia coli. We found that, once assembled, the intermembrane AcrAB-TolC complex is stable during the separation of the inner and outer membranes and subsequent purification. All three components of the complex co-purify when the affinity tag is attached to either of the proteins suggesting bi-partite interactions between AcrA, AcrB, and TolC. We show that antibiotics, the substrates of AcrAB-TolC, stabilize interactions within the complex. However, the formation of the AcrAB-TolC complex does not require an input of energy.

PubMed Online version:10.1074/jbc.M402230200

Carrier Proteins/metabolism; Cell Division; Cell Membrane/metabolism; Centrifugation, Density Gradient; Cross-Linking Reagents/pharmacology; Drug Resistance, Multiple; Electrophoresis, Polyacrylamide Gel; Escherichia coli/metabolism; Escherichia coli Proteins/metabolism; Lipoproteins/metabolism; Membrane Proteins/metabolism; Membrane Transport Proteins; Multidrug Resistance-Associated Proteins; Nuclear Proteins/metabolism; Plasmids/metabolism; Protein Structure, Tertiary; Sucrose/pharmacology