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This article has been retracted

Science 23 December 2005:
Vol. 310. no. 5756, pp. 1950 - 1953
DOI: 10.1126/science.1119776
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Reports

X-ray Structure of the EmrE Multidrug Transporter in Complex with a Substrate

Owen Pornillos, Yen-Ju Chen, Andy P. Chen, Geoffrey Chang*

EmrE is a prototype of the Small Multidrug Resistance family of efflux transporters and actively expels positively charged hydrophobic drugs across the inner membrane of Escherichia coli. Here, we report the x-ray crystal structure, at 3.7 angstrom resolution, of one conformational state of the EmrE transporter in complex with a translocation substrate, tetraphenylphosphonium. Two EmrE polypeptides form a homodimeric transporter that binds substrate at the dimerization interface. The two subunits have opposite orientations in the membrane and adopt slightly different folds, forming an asymmetric antiparallel dimer. This unusual architecture likely confers unidirectionality to transport by creating an asymmetric substrate translocation pathway. On the basis of available structural data, we propose a model for the proton-dependent drug efflux mechanism of EmrE.

Department of Molecular Biology, The Scripps Institute, 10550 North Torrey Pines Road, CB-105, Jolla, CA 92037, USA.

* To whom correspondence should be addressed. E-mail: gchang{at}scripps.edu

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