Structural characterization of the EmrAB-TolC efflux complex from E. coli
Narek Yousefian1, Alina Ornik-Cha2, Sylvie Poussard3
1Univ. Bordeaux, CBMN UMR 5248, Bordeaux INP, F-33600 Pessac, France; Institute of Biochemistry, Goethe-University Frankfurt, Max-von-Laue-Str. 9, D-60438 Frankfurt am Main, Germany.
Abstract:
Gram-negative bacteria export a large variety of antimicrobial compounds by forming two-membrane spanning tripartite multidrug efflux systems composed of an inner membrane transporter, an outer membrane channel and a periplasmic adaptor protein. Here we present the co-expression, purification and first electron microscopy insights of the Escherichia coli EmrAB-TolC tripartite Major Facilitator Superfamily (MSF) efflux system as a whole complex stabilized by Amphipol polymer. The structure reveals a 33 nm long complex delineated by the Amphipol belt at both extremities. Comparison of projection structures of EmrAB-TolC and AcrAB-TolC indicates that the outer membrane protein TolC linked to the periplasmic adaptor EmrA protein form an extended periplasmic canal. The overall length of EmrAB-TolC complex is similar to that of AcrAB-TolC with a probable tip-to-tip interaction between EmrA and TolC unveiling how the adaptor protein connects TolC and EmrB embedded in the inner membrane.
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