Figure 9: Effect of acidic residue substitutions on resistance against dications by QacA and MdfA.
From: Export of a single drug molecule in two transport cycles by a multidrug efflux pump
The experiments were done as in Figs 1b and 5. (a) Mdr by E. coli expressing QacA or its D323C mutant. (b) pH dependence of multidrug resistance by E. coli UTmdfA::kan expressing MdfA or its V231E mutant. Resistance to Dmn and DAPI at pH 8 was tested at lower drug concentrations than pH 6.5 to make sure that even low-level resistance is not conferred. The experiments were repeated at least three times and the results shown are representative.
