Figure 3.

EmrE is functional when reconstituted into liposomes: H⁺-driven uptake of the substrate dequalinium²⁺ by EmrE reconstituted into E. coli polar liposomes, as observed by monitoring dequalinium²⁺ fluorescence. Kinetics timecourses were acquired with excitation at 350 nm and emission at 460 nm. At time zero, proteoliposomes at pH 7 are diluted into a buffer of pH 7 (no proton gradient) or pH 8 (proton gradient). After roughly 30 sec, substrate is added. Assay was carried out with 1 μM EmrE and 5 μM (red), 10 μM (blue), and 20 μM (green) dequalinium²⁺ and in the presence (solid line) or absence (dashed line) of a H⁺ gradient.