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Publication Abstract from PubMed

Membrane transporters of the RND superfamily confer multidrug resistance to pathogenic bacteria, and are essential for cholesterol metabolism and embryonic development in humans. We use high-resolution X-ray crystallography and computational methods to delineate the mechanism of the homotrimeric RND-type proton/drug antiporter AcrB, the active component of the major efflux system AcrAB-TolC in Escherichia coli, and one most complex and intriguing membrane transporters known to date. Analysis of wildtype AcrB and four functionally-inactive variants reveals an unprecedented mechanism that involves two remote alternating-access conformational cycles within each protomer, namely one for protons in the transmembrane region and another for drugs in the periplasmic domain, 50 A apart. Each of these cycles entails two distinct types of collective motions of two structural repeats, coupled by flanking alpha-helices that project from the membrane. Moreover, we rationalize how the cross-talk among protomers across the trimerization interface might lead to a more kinetically efficient efflux system.

Coupling of remote alternating-access transport mechanisms for protons and substrates in the multidrug efflux pump AcrB.,Eicher T, Seeger MA, Anselmi C, Zhou W, Brandstatter L, Verrey F, Diederichs K, Faraldo-Gomez JD, Pos KM Elife. 2014 Sep 19;3. doi: 10.7554/eLife.03145. PMID:25248080^[4]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.