FIGURE 1.

S205L is an activatory mutation. A, the S205L mutation complements the growth of K⁺-auxotrophic E. coli on minimal LB medium containing l mm K⁺ (inset). The growth curve shows measurements of culture density in the presence of 1 mm K⁺ over 12 h. Error bars (at some points smaller than the symbols) represent S.E. (n = 3). B, purified S205L protein has a greater functional activity than WT KirBac3.1 in liposomal ⁸⁶Rb⁺ uptake assays (p = 0.03). The bars represent total rubidium uptake (counts/min) at 30 min at pH 7.5. Control represents empty liposomes. Error bars represent S.E. (n = 3).