title: The secondary multidrug transporter LmrP contains multiple drug interaction sites.
abstract: The secondary multidrug transporter LmrP of Lactococcus lactis mediates the efflux of Hoechst 33342 from the cytoplasmic leaflet of the membrane. Kinetic analysis of Hoechst 33342 transport in inside-out membrane vesicles of L. lactis showed that the LmrP-mediated H(+)/Hoechst 33342 antiport reaction obeyed Michaelis-Menten kinetics, with a low apparent affinity constant of 0.63 microM Hoechst 33342 (= 0.5 mmol Hoechst 33342/mol phospholipid). Several drugs significantly inhibited LmrP-mediated Hoechst 33342 transport through a direct interaction with the protein rather than through dissipation of the proton motive force or reduction of the membrane partitioning of Hoechst 33342. The characterization of the mechanism of inhibition of LmrP-mediated Hoechst 33342 transport indicated competitive inhibition by quinine and verapamil, noncompetitive inhibition by nicardipin and vinblastin, and uncompetitive inhibition by TPP(+). The three types of inhibition of LmrP-mediated Hoechst 33342 transport in inside-out membrane vesicles indicate for the first time the presence of multiple drug interaction sites in a secondary multidrug transporter.
authors.affiliation: Department of Microbiology, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Haren, The Netherlands.
authors.forename: M
authors.initials: M
authors.lastname: Putman
authors.forename: L A
authors.initials: LA
authors.lastname: Koole
authors.forename: H W
authors.initials: HW
authors.lastname: van Veen
authors.forename: W N
authors.initials: WN
authors.lastname: Konings
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism*; D001562:Benzimidazoles / Q000037:antagonists & inhibitors / Q000378:metabolism; D001667:Binding, Competitive; D001692:Biological Transport / Q000187:drug effects; D002352:Carrier Proteins / Q000737:chemistry* / Q000378:metabolism*; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D005456:Fluorescent Dyes / Q000378:metabolism; D007700:Kinetics; D013294:Lactococcus lactis; D008051:Lipid Bilayers / Q000378:metabolism; D008565:Membrane Proteins / Q000737:chemistry* / Q000378:metabolism*; D026901:Membrane Transport Proteins; D009529:Nicardipine / Q000378:metabolism / Q000494:pharmacology; D009861:Onium Compounds / Q000378:metabolism / Q000494:pharmacology; D009943:Organophosphorus Compounds / Q000378:metabolism / Q000494:pharmacology; D010743:Phospholipids / Q000378:metabolism; D011803:Quinine / Q000378:metabolism / Q000494:pharmacology; D013050:Spectrometry, Fluorescence; D014700:Verapamil / Q000378:metabolism / Q000494:pharmacology; D014747:Vinblastine / Q000378:metabolism / Q000494:pharmacology; D014750:Vincristine / Q000378:metabolism / Q000494:pharmacology
chemical_list: D001426:Bacterial Proteins; D001562:Benzimidazoles; D002352:Carrier Proteins; D005456:Fluorescent Dyes; D008051:Lipid Bilayers; C096807:LmrP protein, Lactococcus lactis; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; D009861:Onium Compounds; D009943:Organophosphorus Compounds; D010743:Phospholipids; D014750:Vincristine; D014747:Vinblastine; D011803:Quinine; D014700:Verapamil; D009529:Nicardipine; C017807:bisbenzimide ethoxide trihydrochloride; C013289:tetraphenylphosphonium