Table 1.
Boltzmann fit parameters of the voltage-dependent BK channel activation in the presence of auxiliary BKγ wild types, chimeras, and mutants (γ1 or otherwise indicated in the names for other γ subunits) in the virtual absence of intracellular Ca2+
| Expression | Boltzmann fit parameters | ||
| V1/2 | z | n | |
| mv | |||
| BKα alone | 167 ± 2 | 1.26 ± 0.07 | 8 |
| +γ1 | 22 ± 4 | 1.75 ± 0.09 | 7 |
| +γ2 | 61 ± 3 | 1.17 ± 0.07 | 8 |
| +γ3 | 115 ± 2 | 1.36 ± 0.05 | 6 |
| +γ4 | 154 ± 3 | 1.27 ± 0.07 | 7 |
| +β1 | 197 ± 6 | 0.80 ± 0.02 | 3 |
| +β1(2–155)/ γ1(258–298) | 23 ± 2 | 1.04 ± 0.05 | 7 |
| +β1(2–155)/ γ1(258–298)F273S/V275A | 149 ± 6 | 0.96 ± 0.09 | 6 |
| +Δ262–265 | 152 ± 2 | 1.36 ± 0.01 | 3 |
| +Δ266–269 | 159 ± 6 | 1.38 ± 0.10 | 4 |
| +Δ270–273 | 157 ± 7 | 1.32 ± 0.09 | 7 |
| +Δ274–279 | 163 ± 6 | 1.23 ± 0.09 | 5 |
| +Δ280–284 | 166 ± 7 | 1.13 ± 0.08 | 6 |
| +Δ285–289 | 27 ± 3 | 1.12 ± 0.10 | 4 |
| +γ1/γ2-tail | 143 ± 3 | 1.26 ± 0.05 | 4 |
| +γ1/γ2-linker&tail | 60 ± 5 | 1.09 ± 0.07 | 3 |
| +γ1/γ4-tail | 147 ± 3 | 1.23 ± 0.08 | 5 |
| +γ1/γ4-linker&tail | 97 ± 3 | 1.03 ± 0.03 | 5 |
| +γ1/γ4-TMa | 69 ± 3 | 1.33 ± 0.05 | 3 |
| +γ1/γ4-TMb | 164 ± 5 | 1.29 ± 0.03 | 3 |
| +γ1/γ4-TMc | 59 ± 3 | 1.11 ± 0.09 | 4 |
| +γ1/γ4-TMd | 67 ± 4 | 1.22 ± 0.05 | 9 |
| +γ1/γ4-TMF273 | 103 ± 3 | 1.12 ± 0.07 | 5 |
| +γ1/γ4-TM | 155 ± 4 | 1.30 ± 0.03 | 5 |
| +γ2-F256S | 165 ± 4 | 1.26 ± 0.05 | 9 |
| +γ2-F256Sa | 159 ± 3 | 1.31 ± 0.07 | 5 |
| +γ3-S282F | 100 ± 3 | 1.54 ± 0.10 | 4 |
| +γ4-S259F | 125 ± 2 | 1.23 ± 0.09 | 4 |
| +P270F | 16 ± 2 (83%)b120 ± 9 (17%)c | 1.51 ± 0.061.04 ± 0.20c | 10 |
| +P270Fa | 22 ± 2 (91%)138 ± 14 (9%)c | 1.63 ± 0.081.22 ± 0.79c | 9 |
| +A271V | 1 ± 3 | 1.36 ± 0.16 | 3 |
| +S272V | 67 ± 2 | 1.07 ± 0.04 | 3 |
| +F273S | 18 ± 1 (79%)126 ± 8 (21%)c | 1.55 ± 0.070.99 ± 0.16c | 13 |
| +F273Sa | 20 ± 1 (91%)117 ± 17 (9%)c | 1.80 ± 0.111.36 ± 1.0c | 7 |
| +L274A | 25 ± 4 | 1.43 ± 0.13 | 3 |
| +V275A | 26 ± 2 | 1.60 ± 0.13 | 3 |
| +P270V/F273S | 155 ± 2 | 1.48 ± 0.14 | 5 |
| +P270V/F273Sa | 150 ± 3 | 1.27 ± 0.05 | 8 |
| +S272V/F273S | 65 ± 3 (80%)163 ± 3 (20%)c | 1.26 ± 0.11.75 ± 0.35c | 5 |
| +F273S/L274A | 157 ± 2 | 1.25 ± 0.19 | 3 |
| +F273S/L274Aa | 152 ± 2 | 1.31 ± 0.06 | 5 |
| +F273S/V275A | 152 ± 2 | 1.14 ± 0.07 | 4 |
| +F273S/V275Aa | 145 ± 3 | 1.33 ± 0.07 | 6 |
| +Δ3R | 40 ± 1 | 1.34 ± 0.05 | 4 |
| +Δ3R/R293Q | 138 ± 2 | 1.35 ± 0.08 | 4 |
| +Δ3R/R293Qa | 12 ± 3 | 1.30 ± 0.10 | 2 |
| 23 ± 3 (46%)139 ± 4 (54%) | 1.55 ± 0.140.88 ± 0.11 | 5 | |
| 152 | 1.61 | 1 | |
| +Δ4R | 146 ± 4 | 1.15 ± 0.05 | 11 |
| +Δ4Ra | 48 ± 2 | 1.70 ± 0.11 | 4 |
| 48 ± 3 (32%)c141 ± 5 (68%) | 2.02 ± 0.39c0.93 ± 0.08 | 4 | |
| 162 ± 6 | 1.13 ± 0.18 | 2 | |
| +Δ3R/R293K | 35 ± 2 (67%)144 ± 4 (33%)c | 1.19 ± 0.061.16 ± 0.12c | 6 |
| 33 ± 11 (11%)c145 ± 2 (89%) | 1.04 ± 0.22c1.12 ± 0.02 | 4 | |
| +Δ3R/R291Q | 49 ± 3 (79%)147 ± 9 (19%)c | 1.22 ± 0.111.58 ± 0.54c | 3 |
| 53 (47%)154 (53%) | 1.071.26 | 1 | |
| 154 ± 7 | 1.31 ± 0.07 | 3 | |
| +Δ3R/R291Qa | 47 ± 2 (69%)159 ± 4 (31%)c | 1.41 ± 0.101.68 ± 0.27c | 3 |
| 32 ± 34 (10%)c138 ± 5 (90%) | 1.01 ± 0.55c0.89 ± 0.10 | 5 | |
| 141 ± 6 | 1.14 ± 0.0.14 | 4 | |
| +Δ3R/R291K | 24 ± 3 | 1.60 ± 0.10 | 3 |
| 38 ± 8 (69%)134 ± 23 (31%)c | 1.21 ± 0.200.98 ± 0.37c | 3 | |
| 33 ± 3 (27%)c158 ± 2 (73%) | 1.79 ± 0.28c1.17 ± 0.09 | 2 | |
| +Δ3R/R298Q | 37 ± 2 | 1.14 ± 0.10 | 2 |
| 53 ± 3 (79%)137 ± 8 (21%)c | 1.62 ± 0.141.93 ± 0.93c | 5 | |
| 57 ± 5 (43%)142 ± 5 (57%) | 1.35 ± 0.171.16 ± 0.18 | 5 | |
| 153 ± 2 | 0.94 ± 0.04 | 4 | |
| +Δ3R/R298Qa | 49 ± 2 (82%)129 ± 13 (18%)c | 1.87 ± 0.091.01 ± 0.34c | 9 |
| 48 ± 5 (26%)c138 ± 3 (74%) | 1.64 ± 0.28c1.15 ± 0.07 | 3 | |
| 175 | 1.00 | 1 | |
| +Δ3R/R298K | 21 ± 4 | 1.35 ± 0.08 | 5 |
| 30 ± 3 (48%)123 ± 14 (54%) | 1.70 ± 0.320.81 ± 0.30 | 5 | |
| 175 | 1.00 | 1 | |
| +F273S/Δ3R | 163 ± 7 | 1.13 ± 0.04 | 5 |
| +F273S/Δ3Ra | 157 ± 4 | 1.48 ± 0.07 | 5 |
| +P270F/Δ4R | 65 ± 2 | 1.07 ± 0.04 | 5 |
| ΔtailN291–298 | 168 ± 3 | 1.22 ± 0.11 | 5 |
| ΔtailN291–298a | 172 ± 5 | 1.34 ± 0.05 | 4 |
n values are the number of recorded excised inside-out patches from different HEK-293 cells.
The indicated γ subunit mutant was overexpressed relative to BKα.
The indicated percentage in parentheses here and elsewhere refers to the portion of the channels’ subpopulation that was obtained from a double Boltzmann function fit.
Because of the difficulty in obtaining reliable parameter values from a double Boltzmann function fit for the minor portion (e.g., ≤35%), the estimated values of the V1/2 and errors provided here are considered less reliable and used for references only.