FIG. 4.

Activation of KdpD, KdpD-C, and C499-894 is specific for K⁺. HAK006 cells producing KdpD (A), KdpD-C (B), or C499-894 (C) were grown to mid-logarithmic phase in minimal medium containing 6 mM KCl. Cells were washed with minimal medium containing 0.1 mM KCl and transferred into fresh medium containing 0.1 mM KCl. Then, 6 mM RbCl or 6 mM LiCl was added. A control culture was resuspended in medium containing 6 mM KCl. The β-galactosidase activity was determined at the indicated time points and normalized to the maximum β-galactosidase activity (100% of control Miller units) of the KdpD⁺ culture growing in medium containing 0.1 mM KCl.