Phosphorylation of CLH-3b alters the kinetics of hyperpolarization-induced channel activation. Time constants describing activation kinetics of CLH-3b (A) and the S742E, S747E mutant channel (B) in response to hyperpolarizing voltage steps. Wild-type and mutant channels were coexpressed with KD or functional GCK-3. Values are means ± SE (n = 7–12).