Mutation of S742 to alanine prevents GCK-3–mediated inhibition of CLH-3b. (A) Current-to-voltage relationships of the S742A mutant coexpressed with functional or KD GCK-3. Values are means ± SE (n = 7). (B) Activation voltages and 50% rise times of whole cell currents in cells coexpressing the S742A mutant and KD GCK-3 or GCK-3. Values are means ± SE (n = 7). (C) Effect of cell swelling on current amplitude in cells coexpressing the S742A mutant and KD GCK-3 or GCK-3. Values are means ± SE (n = 7). Data were obtained as described in the legend to Fig. 1.