title: Three-dimensional structure of the bacterial multidrug transporter EmrE shows it is an asymmetric homodimer.
abstract: The small multidrug resistance family of transporters is widespread in bacteria and is responsible for bacterial resistance to toxic aromatic cations by proton-linked efflux. We have determined the three-dimensional (3D) structure of the Escherichia coli multidrug transporter EmrE by electron cryomicroscopy of 2D crystals, including data to 7.0 A resolution. The structure of EmrE consists of a bundle of eight transmembrane alpha-helices with one substrate molecule bound near the centre. The substrate binding chamber is formed from six helices and is accessible both from the aqueous phase and laterally from the lipid bilayer. The most remarkable feature of the structure of EmrE is that it is an asymmetric homodimer. The possible arrangement of the two polypeptides in the EmrE dimer is discussed based on the 3D density map.
authors.affiliation: MRC Laboratory of Molecular Biology, Hills Road, Cambridge CB2 2QH, UK.
authors.forename: Iban
authors.initials: I
authors.lastname: Ubarretxena-Belandia
authors.forename: Joyce M
authors.initials: JM
authors.lastname: Baldwin
authors.forename: Shimon
authors.initials: S
authors.lastname: Schuldiner
authors.forename: Christopher G
authors.initials: CG
authors.lastname: Tate
mesh_terms: D017920:Antiporters / Q000737:chemistry* / Q000378:metabolism; D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism; D001692:Biological Transport; D018360:Crystallography, X-Ray / Q000379:methods; D019281:Dimerization; D004926:Escherichia coli / Q000378:metabolism; D029968:Escherichia coli Proteins; D007091:Image Processing, Computer-Assisted; D008565:Membrane Proteins / Q000737:chemistry* / Q000378:metabolism; D008954:Models, Biological; D008958:Models, Molecular; D011487:Protein Conformation; D017433:Protein Structure, Secondary
chemical_list: D017920:Antiporters; D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D008565:Membrane Proteins; C075436:EmrE protein, E coli