Figure 2. Inhibition of multidrug efflux by verapamil.

(a,b) The inhibition of bacterial growth as monitored by attenuance at 600 nm. The bacteria expressing the MATE variants or pET-15b were grown in the presence of 150 μM (∼74 μg ml⁻¹) verapamil (a); or in the presence of 0.5 μg ml⁻¹ of ethidium, with or without 50 μM verapamil (b). (c) R6G accumulation in bacteria expressing the MATE variants or pET-15b in the absence (magenta) or presence of 100 μM verapamil (yellow), or 25 μM CCCP (white), as examined by the measurement of R6G fluorescence. Error bars indicate s.d. among three biological replicates.