Functional analyses of the amino acids within the poly-Arg cluster region and their relationship with the TM segment. (A–D) Voltage dependence of BK channel activation in the presence of different BKγ1 mutants with mutations in the poly-Arg cluster region. For mutants that produced heterogeneity in BK channel gating properties, membrane patches with similar channel G-V relationship were grouped together and indicated in the label with the number of grouped membrane patches over total recorded membrane patches. (E and F) Voltage dependence of BK channel activation in the presence of BKγ1 mutants with single mutation from the TM segment and poly-Arg cluster region and with combined double mutation from both regions. Error bars represent ±SEM.