title: Crystal structure of bacterial multidrug efflux transporter AcrB.
abstract: AcrB is a major multidrug exporter in Escherichia coli. It cooperates with a membrane fusion protein, AcrA, and an outer membrane channel, TolC. We have determined the crystal structure of AcrB at 3.5 A resolution. Three AcrB protomers are organized as a homotrimer in the shape of a jellyfish. Each protomer is composed of a transmembrane region 50 A thick and a 70 A protruding headpiece. The top of the headpiece opens like a funnel, where TolC might directly dock into AcrB. A pore formed by three alpha-helices connects the funnel with a central cavity located at the bottom of the headpiece. The cavity has three vestibules at the side of the headpiece which lead into the periplasm. In the transmembrane region, each protomer has twelve transmembrane alpha-helices. The structure implies that substrates translocated from the cell interior through the transmembrane region and from the periplasm through the vestibules are collected in the central cavity and then actively transported through the pore into the TolC tunnel.
authors.affiliation: Department of Cell Membrane Biology, Institute of Scientific and Industrial Research, Osaka University, Ibaraki, Osaka 567-0047, Japan.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Murakami
authors.forename: Ryosuke
authors.initials: R
authors.lastname: Nakashima
authors.forename: Eiki
authors.initials: E
authors.lastname: Yamashita
authors.forename: Akihito
authors.initials: A
authors.lastname: Yamaguchi
mesh_terms: D001425:Bacterial Outer Membrane Proteins / Q000737:chemistry / Q000378:metabolism; D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism; D001692:Biological Transport; D002352:Carrier Proteins; D002462:Cell Membrane / Q000737:chemistry; D018360:Crystallography, X-Ray; D024901:Drug Resistance, Multiple, Bacterial; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000378:metabolism; D008565:Membrane Proteins / Q000737:chemistry* / Q000378:metabolism; D026901:Membrane Transport Proteins; D008958:Models, Molecular; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D011485:Protein Binding; D011487:Protein Conformation; D017434:Protein Structure, Tertiary
chemical_list: D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D002352:Carrier Proteins; D029968:Escherichia coli Proteins; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; D027425:ATP-Binding Cassette, Sub-Family C Proteins; C083496:AcrB protein, E coli; C073126:tolC protein, E coli