Figure 4.

The effects of Ca²⁺ and charge neutralization of the Ca²⁺-bowl site on BKα channel modulation by the synthetic γ peptide mimics. (A) Representative current traces of BKα WT (no label) and 5D5N mutant channels in response to depolarization of the membrane potential from −80 or −160 mV in 20-mV steps for selected expression constructs. (B) The overlayed inward tail currents of BKα WT and 5D5N mutant channels before and after application of 20 µM γ1 peptide. Currents elicited by activation at all voltages, 140 mV, and 240 mV are shown from left to right. The current data were low-pass filtered at 10 kHz. (C) Voltage dependence of BKα channel activation in the presence of 20 µM γ1 peptide at 20 µM and 1 mM Ca²⁺. (D–F) Voltage dependence of BKα 5D5N mutant channel activation in the presence of the 20 µM γ1 (D), γ2 (E), or γ3 (F) peptide at virtual 0 Ca²⁺. Error bars represent ± SEM.