New insights into the structure and oligomeric state of the bacterial multidrug transporter EmrE: an unusual asymmetric homo-dimer.
EmrE is a small multidrug transporter that contains 110 amino acid residues that form four transmembrane alpha-helices. The three-dimensional structure of EmrE has been determined from two-dimensional crystals by electron cryo-microscopy. EmrE is an asymmetric homo-dimer with one substrate molecule bound in a chamber accessible laterally from one leaflet of the lipid bilayer. Evidence from substrate binding analyses and analytical ultracentrifugation of detergent-solubilised EmrE shows that the minimum functional unit for substrate binding is a dimer. However, it is possible that EmrE exists as a tetramer in vivo and plausible models are suggested based upon analyses of two-dimensional crystals.
Ubarretxena-Belandia
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MRC Laboratory of Molecular Biology, Hills Road, Cambridge CB2 2QH, UK.
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D017920:Antiporters / Q000737:chemistry* / Q000378:metabolism; D019281:Dimerization; D004352:Drug Resistance, Microbial; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000378:metabolism; D008051:Lipid Bilayers / Q000737:chemistry / Q000378:metabolism; D008565:Membrane Proteins / Q000737:chemistry* / Q000378:metabolism; D008958:Models, Molecular; D020836:Protein Structure, Quaternary; D017433:Protein Structure, Secondary
D017920:Antiporters; D029968:Escherichia coli Proteins; D008051:Lipid Bilayers; D008565:Membrane Proteins; C075436:EmrE protein, E coli