Manipulating the drug/proton antiport stoichiometry of the secondary multidrug transporter MdfA.
Multidrug transporters are integral membrane proteins that use cellular energy to actively extrude antibiotics and other toxic compounds from cells. The multidrug/proton antiporter MdfA from Escherichia coli exchanges monovalent cationic substrates for protons with a stoichiometry of 1, meaning that it translocates only one proton per antiport cycle. This may explain why transport of divalent cationic drugs by MdfA is energetically unfavorable. Remarkably, however, we show that MdfA can be easily converted into a divalent cationic drug/≥ 2 proton-antiporter, either by random mutagenesis or by rational design. The results suggest that exchange of divalent cationi c drugs with two (or more) protons requires an additional acidic residue in the multidrug recognition pocket of MdfA. This outcome further illustrates the exceptional promiscuous capabilities of multidrug transporters.
Department of Biological Chemistry,  The Weizmann Institute of Science, Rehovot 76100,  Israel.
Osnat
O
Tirosh
Nadejda
N
Sigal
Amir
A
Gelman
Nadav
N
Sahar
Nir
N
Fluman
Shira
S
Siemion
Eitan
E
Bibi
D004352:Drug Resistance, Microbial / Q000502:physiology; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism*; D017136:Ion Transport / Q000502:physiology; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism*; D016296:Mutagenesis; D011522:Protons
D029968:Escherichia coli Proteins; C118438:Mdfa protein, E coli; D026901:Membrane Transport Proteins; D011522:Protons