title: Crystal structures of a multidrug transporter reveal a functionally rotating mechanism.
abstract: AcrB is a principal multidrug efflux transporter in Escherichia coli that cooperates with an outer-membrane channel, TolC, and a membrane-fusion protein, AcrA. Here we describe crystal structures of AcrB with and without substrates. The AcrB-drug complex consists of three protomers, each of which has a different conformation corresponding to one of the three functional states of the transport cycle. Bound substrate was found in the periplasmic domain of one of the three protomers. The voluminous binding pocket is aromatic and allows multi-site binding. The structures indicate that drugs are exported by a three-step functionally rotating mechanism in which substrates undergo ordered binding change.
authors.affiliation: Department of Cell Membrane Biology, Institute of Scientific and Industrial Research, Osaka University, Ibaraki, Osaka 567-0047, Japan. mura@sanken.osaka-u.ac.jp
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: Takashi
authors.initials: T
authors.lastname: Matsumoto
authors.forename: Akihito
authors.initials: A
authors.lastname: Yamaguchi
mesh_terms: D001425:Bacterial Outer Membrane Proteins / Q000378:metabolism; D001665:Binding Sites; D002462:Cell Membrane / Q000378:metabolism; D018360:Crystallography, X-Ray; D004926:Escherichia coli / Q000737:chemistry; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000378:metabolism*; D008074:Lipoproteins / Q000378:metabolism; D026901:Membrane Transport Proteins; D008911:Minocycline / Q000737:chemistry / Q000378:metabolism; D008954:Models, Biological; D008958:Models, Molecular; D027425:ATP-Binding Cassette, Sub-Family C Proteins / Q000737:chemistry* / Q000378:metabolism*; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D012399:Rotation; D013329:Structure-Activity Relationship; D013379:Substrate Specificity
chemical_list: D001425:Bacterial Outer Membrane Proteins; D029968:Escherichia coli Proteins; D008074:Lipoproteins; D026901:Membrane Transport Proteins; D008911:Minocycline; D027425:ATP-Binding Cassette, Sub-Family C Proteins; C083497:AcrA protein, E coli; C083496:AcrB protein, E coli; C073126:tolC protein, E coli