title: Energetics and mechanism of drug transport mediated by the lactococcal multidrug transporter LmrP.
abstract: The gene encoding the secondary multidrug transporter LmrP of Lactococcus lactis was heterologously expressed in Escherichia coli. The energetics and mechanism of drug extrusion mediated by LmrP were studied in membrane vesicles of E. coli. LmrP-mediated extrusion of tetraphenyl phosphonium (TPP+) from right-side-out membrane vesicles and uptake of the fluorescent membrane probe 1-[4-(trimethylamino)phenyl]-6-phenylhexa-1,3,5-triene (TMA-DPH) into inside-out membrane vesicles are driven by the membrane potential (Deltapsi) and the transmembrane proton gradient (DeltapH), pointing to an electrogenic drug/proton antiport mechanism. Ethidium bromide, a substrate for LmrP, inhibited the LmrP-mediated TPP+ extrusion from right-side-out membrane vesicles, showing that LmrP is capable of transporting structurally unrelated drugs. Kinetic analysis of LmrP-mediated TMA-DPH transport revealed a direct relation between the transport rate and the amount of TMA-DPH associated with the cytoplasmic leaflet of the lipid bilayer. This observation indicates that drugs are extruded from the inner leaflet of the cytoplasmic membrane into the external medium. This is the first report that shows that drug extrusion by a secondary multidrug resistance (MDR) transporter occurs by a "hydrophobic vacuum cleaner" mechanism in a similar way as was proposed for the primary lactococcal MDR transporter, LmrA.
authors.affiliation: Department of Microbiology, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Kerklaan 30, NL-9751 NN Haren, The Netherlands.
authors.forename: H
authors.initials: H
authors.lastname: Bolhuis
authors.forename: H W
authors.initials: HW
authors.lastname: van Veen
authors.forename: J R
authors.initials: JR
authors.lastname: Brands
authors.forename: M
authors.initials: M
authors.lastname: Putman
authors.forename: B
authors.initials: B
authors.lastname: Poolman
authors.forename: A J
authors.initials: AJ
authors.lastname: Driessen
authors.forename: W N
authors.initials: WN
authors.lastname: Konings
mesh_terms: D001426:Bacterial Proteins / Q000378:metabolism*; D001692:Biological Transport; D002352:Carrier Proteins / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D002474:Cell-Free System; D004161:Diphenylhexatriene / Q000031:analogs & derivatives / Q000378:metabolism; D018432:Drug Resistance, Multiple; D004734:Energy Metabolism; D007700:Kinetics; D013294:Lactococcus lactis; D008564:Membrane Potentials; D008565:Membrane Proteins / Q000378:metabolism*; D026901:Membrane Transport Proteins; D009861:Onium Compounds / Q000378:metabolism; D009943:Organophosphorus Compounds / Q000378:metabolism; D011994:Recombinant Proteins
chemical_list: D001426:Bacterial Proteins; D002352:Carrier Proteins; C096807:LmrP protein, Lactococcus lactis; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; D009861:Onium Compounds; D009943:Organophosphorus Compounds; D011994:Recombinant Proteins; D004161:Diphenylhexatriene; C033628:1-(4-(trimethylamino)phenyl)-6-phenylhexa-1,3,5-triene; C013289:tetraphenylphosphonium