title: The ATP binding cassette multidrug transporter LmrA and lipid transporter MsbA have overlapping substrate specificities.
abstract: LmrA is an ATP binding cassette (ABC) multidrug transporter in Lactococcus lactis that is a structural and functional homologue of the human multidrug resistance P-glycoprotein MDR1 (ABCB1). LmrA is also homologous to MsbA, an essential ABC transporter in Escherichia coli involved in the trafficking of lipids, including Lipid A. We have compared the substrate specificities of LmrA and MsbA in detail. Surprisingly, LmrA was able to functionally substitute for a temperature-sensitive mutant MsbA in E. coli WD2 at non-permissive temperatures, suggesting that LmrA could transport Lipid A. LmrA also exhibited a Lipid A-stimulated, vanadate-sensitive ATPase activity. Reciprocally, the expression of MsbA conferred multidrug resistance on E. coli. Similar to LmrA, MsbA interacted with photoactivatable substrate [3H]azidopine, displayed a daunomycin, vinblastine, and Hoechst 33342-stimulated vanadate-sensitive ATPase activity, and mediated the transport of ethidium from cells and Hoechst 33342 in proteoliposomes containing purified and functionally reconstituted protein. Taken together, these data demonstrate that MsbA and LmrA have overlapping substrate specificities. Our observations imply the presence of structural elements in the recently published crystal structures of MsbA in E. coli and Vibrio cholera (Chang, G., and Roth, C. B. (2001) Science 293, 1793-1800; Chang, G. (2003) J. Mol. Biol. 330, 419-430) that support drug-protein interactions and suggest a possible role for LmrA in lipid trafficking in L. lactis.
authors.affiliation: Department of Pharmacology, University of Cambridge, Cambridge CB2 1PD, United Kingdom.
authors.forename: Galya
authors.initials: G
authors.lastname: Reuter
authors.forename: Tavan
authors.initials: T
authors.lastname: Janvilisri
authors.forename: Henrietta
authors.initials: H
authors.lastname: Venter
authors.forename: Sanjay
authors.initials: S
authors.lastname: Shahi
authors.forename: Lekshmy
authors.initials: L
authors.lastname: Balakrishnan
authors.forename: Hendrik W
authors.initials: HW
authors.lastname: van Veen
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000378:metabolism; D018528:ATP-Binding Cassette Transporters / Q000378:metabolism; D001426:Bacterial Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D001692:Biological Transport; D018432:Drug Resistance, Multiple; D004996:Ethidium / Q000493:pharmacokinetics; D006801:Humans; D007700:Kinetics; D013294:Lactococcus lactis / Q000254:growth & development / Q000378:metabolism*; D027425:ATP-Binding Cassette, Sub-Family C Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D018528:ATP-Binding Cassette Transporters; D001426:Bacterial Proteins; D004996:Ethidium; D027425:ATP-Binding Cassette, Sub-Family C Proteins; C101824:LmrA protein, Lactococcus lactis