Fig. 6.
Sodium ion enhances sulfamethazine efflux via YdaH. (a) Accumulation of radioactive sulfamethazine in BL21(DE3)ΔabgTΔpabA/pET15bΩydaH cells with difference sodium ion concentrations. Cells showed a significant decrease in [3H]-sulfamethazine accumulation in the presence of Na+. Error bars denote standard deviation (n = 3). “*” indicates values of BL21(DE3)ΔabgTΔpabA/pET15b cells (control) that are significantly different from those of BL21(DE3) ΔabgTΔpabA/pET15bΩydaH expressing wild-type YdaH (P < 0.001; student’s t-test). (b) Efflux of radioactive sulfamethazine in BL21(DE3)ΔabgTΔpabA/pET15bΩydaH cells in the presence of sodium or potassium ions. The presence of Na+ significantly enhances [3H]-sulfamethazine efflux in BL21(DE3)ΔabgTΔpabA/pET15bΩydaH cells (black, control cells with the empty vector; red, 0 mM NaCl; magenta, 5 mM KCl; blue, 5 mM NaCl). Error bars denote standard deviation (n = 3). “*” indicates values of radioactive counts of intracellular [3H]-sulfamethazine in BL21(DE3)ΔabgTΔpabA/pET15bΩydaH cells with 5 mM NaCl (blue) that are significantly different from those of the control (black) (P < 0.001; student’s t-test).