The projection structure of EmrE, a proton-linked multidrug transporter from Escherichia coli, at 7 A resolution.
EmrE belongs to a family of eubacterial multidrug transporters that confer resistance to a wide variety of toxins by coupling the influx of protons to toxin extrusion. EmrE was purified and crystallized in two dimensions by reconstitution with dimyristoylphosphatidylcholine into lipid bilayers. Images of frozen hydrated crystals were collected by cryo-electron microscopy and a projection structure of EmrE was calculated to 7 A resolution. The projection map shows an asymmetric EmrE dimer with overall dimensions approximately 31 x 40 A, comprising an arc of highly tilted helices separating two helices nearly perpendicular to the membrane from another two helices, one tilted and the other nearly perpendicular. There is no obvious 2-fold symmetry axis perpendicular to the membrane within the dimer, suggesting that the monomers may have different structures in the functional unit.
MRC Laboratory of Molecular Biology, Hills Road, Cambridge CB2 2QH, MRC Dunn Human Nutrition Unit, Hills Road, Cambridge CB2 2XY, UK.
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D017920:Antiporters / Q000737:chemistry* / Q000648:ultrastructure*; D001426:Bacterial Proteins / Q000737:chemistry / Q000648:ultrastructure; D020285:Cryoelectron Microscopy; D018360:Crystallography, X-Ray / Q000379:methods; D019281:Dimerization; D004134:Dimyristoylphosphatidylcholine; D018432:Drug Resistance, Multiple; D004926:Escherichia coli / Q000502:physiology*; D029968:Escherichia coli Proteins; D008051:Lipid Bilayers; D008565:Membrane Proteins / Q000737:chemistry* / Q000648:ultrastructure*; D017433:Protein Structure, Secondary; D011994:Recombinant Proteins / Q000737:chemistry / Q000648:ultrastructure
D017920:Antiporters; D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D008051:Lipid Bilayers; D008565:Membrane Proteins; D011994:Recombinant Proteins; C075436:EmrE protein, E coli; D004134:Dimyristoylphosphatidylcholine