Figure 5

Ethidium transport by SbMATE is proton-dependent and is selective against transporting the divalent organic cation, propidium. (A) The ethidium transport assay was performed at varying extracellular pH conditions, while maintaining the same salt content as in Fig. 2B. The transport rate was calculated as described for Fig. 2C, with the rate at pH 8.5 set to 100% (n = 3 independent replicates, data are mean ± SEM). The pH 4.3 assay conditions were obtained using 20 mM citrate buffer. (B) Chemical structures of (i) ethidium (+1) and (ii) propidium (+2) reveal a high degree of similarity, except for the additional charged moiety on propidium. (C) Transport assay was performed as described in Fig. 2A, except with 50 or 100 µM of propidium iodide (PI) instead of ethidium bromide. Histograms are shown for induced SbMATE WT-expressing or non-expressing control cells (n = 3). (D) Graph was generated as described in Fig. 2B for induced SbMATE-expressing cells. Data from the transport assay performed with 100 µM ethidium bromide is shown for comparison. For data with 50 µM ethidium bromide, see Fig. 2C (n = 3 independent replicates, data are mean ± SEM).