Figure 4.  Transport systems coupled to .  The data shown are for lactose accumu­lation by RSO vesicles con­taining the lactose permease, but similar profiles are observed for proline, serine, glycine, tyro­sine, glutamic acid, lysine, leucine, cysteine and succinate (a dicarboxylic acid).  At pH 5.5, accumulation of each of these substrates is relatively mildly inhibited by both valinomycin and nigericin, while at pH 7.5, valinomycin becomes a potent inhibitor and nigericin has no effect.  The profiles  resemble that observed for the total driving force () in Fig. 3.