title: Export of a single drug molecule in two transport cycles by a multidrug efflux pump.
abstract: Secondary multidrug transporters use ion concentration gradients to energize the removal from cells of various antibiotics. The Escherichia coli multidrug transporter MdfA exchanges a single proton with a single monovalent cationic drug molecule. This stoichiometry renders the efflux of divalent cationic drugs energetically unfavourable, as it requires exchange with at least two protons. Here we show that surprisingly, MdfA catalyses efflux of divalent cations, provided that they have a unique architecture: the two charged moieties must be separated by a long linker. These drugs are exchanged for two protons despite the apparent inability of MdfA to exchange two protons for a single drug molecule. Our results suggest that these drugs are transported in two consecutive transport cycles, where each cationic moiety is transported as if it were a separate substrate. We propose that secondary transport can adopt a processive-like mode of action, thus expanding the substrate spectrum of multidrug transporters.
authors.affiliation: 1] Department of Biological Chemistry, Weizmann Institute of Science, Rehovot 76100, Israel [2].
authors.forename: Nir
authors.initials: N
authors.lastname: Fluman
authors.affiliation: 1] Department of Biological Chemistry, Weizmann Institute of Science, Rehovot 76100, Israel [2].
authors.forename: Julia
authors.initials: J
authors.lastname: Adler
authors.affiliation: Department of Chemistry and Biochemistry, Queens College-City University of New York, Flushing, New York 11367, USA.
authors.forename: Susan A
authors.initials: SA
authors.lastname: Rotenberg
authors.affiliation: School of Biological Sciences, Flinders University, Adelaide South Australia 5001, Australia.
authors.forename: Melissa H
authors.initials: MH
authors.lastname: Brown
authors.affiliation: Department of Biological Chemistry, Weizmann Institute of Science, Rehovot 76100, Israel.
authors.forename: Eitan
authors.initials: E
authors.lastname: Bibi
mesh_terms: D001692:Biological Transport; D002384:Catalysis; D002412:Cations; D003432:Cross-Linking Reagents / Q000737:chemistry; D003868:Dequalinium / Q000737:chemistry; D004305:Dose-Response Relationship, Drug; D024901:Drug Resistance, Multiple, Bacterial; D004926:Escherichia coli / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism*; D009154:Mutation; D010957:Plasmids / Q000378:metabolism; D011522:Protons
chemical_list: D002412:Cations; D003432:Cross-Linking Reagents; D029968:Escherichia coli Proteins; C118438:Mdfa protein, E coli; D026901:Membrane Transport Proteins; D011522:Protons; D003868:Dequalinium