Table 1.
Gating Parameters of the K+ Channel Mutants Studied
| Mutants | Imax | Rise time | τi | τc | ||||
|---|---|---|---|---|---|---|---|---|
| nA | n | ms | n | ms | n | ms | n | |
| WT | 3.3 ± 2.3 | 9 | 1.44 ± 0.5 | 9 | 2190 ± 250 | 6 | 1.53 ± 0.45 | 8 |
| E251Q | 3.8 ± 2.5 | 8 | 0.93 ± 0.3 | 4 | 1980 ± 140 | 4 | 1.10 ± 0.30 | 3 |
| D277N | 2.7 ± 1.5 | 10 | 0.96 ± 0.3 | 6 | 1770 ± 750 | 5 | 0.97 ± 0.25 | 3 |
| 4Q | 3.4 ± 1.7 | 12 | 1.84 ± 0.4 | 7 | 2400 ± 640 | 8 | — | |
| 5Q | 4.2 ± 3.1 | 23 | 1.84 ± 0.6 | 14 | 1490 ± 950 | 9 | 2.38 ± 0.36 | 3 |
| 6Q | 0.29 ± 0.21 | 16* | 1.27 ± 0.41 | 8 | 11.2 ± 2.70 | 7* | — | |
| E418Q | 0.45 ± 0.49 | 15* | 1.12 ± 0.2 | 7 | 9.22 ± 2.40 | 6* | 0.35 ± 0.06 | 4* |
| E418D | 4.9 ± 3.1 | 17 | 1.36 ± 0.5 | 10 | 2600 ± 120 | 7 | 2.31 ± 0.51 | 3 |
Mean ± SD; n, number of experiments. *Parameters are significantly different (P < 0.001, nonparametric Mann-Whitney U test) from the values in the wild-type channel. Peak current amplitude (Imax), rise time (time between 20 and 80% of current amplitude), and inactivation time constant (τi) were measured at +20 mV. Closing time constant (τc) was measured at −80 mV in 30 mM external K+.