Activation and Inactivation Parameters of Wild-type and Mutant Kv4.2 Channels
| IP,+40 (µA) | f+40 | n | V1/2,act (mV) | sact (mV) | n | V1/2,inact (mV) | sinact (mV) | n | |
| wt | 3.8 ± 0.6 | 0.042 ± 0.005 | 7 | +7.5 ± 0.7 | 20.4 ± 0.7 | 7 | −66.9 ± 0.8 | 5.9 ± 0.3 | 9 |
| G309A | 11.5 ± 1.1 | 0.425 ± 0.020 | 5 | −1.7 ± 1.1 | 22.3 ± 0.1 | 5 | −74.7 ± 0.9 | 5.2 ± 0.2 | 5 |
| L310A | 1.4 ± 0.3 | 0.148 ± 0.025 | 9 | +131 ± 19 | 62.0 ± 7.3 | 4 | −19.7 ± 0.4 | 12.1 ± 0.6 | 3 |
| R311A | 3.9 ± 0.6 | 0.020 ± 0.011 | 5 | +26.1 ± 2.3 | 22.9 ± 0.8 | 5 | −48.2 ± 2.1 | 5.8 ± 0.1 | 5 |
| I312A | 13.9 ± 1.7 | 0.224 ± 0.018 | 5 | +13.8 ± 2.0 | 20.7 ± 0.3 | 5 | −72.3 ± 1.1 | 7.7 ± 0.4 | 5 |
| L313A | 3.3 ± 0.4 | 0.011 ± 0.007 | 5 | +12.0 ± 0.3 | 25.0 ± 0.2 | 5 | −77.5 ± 0.4 | 7.0 ± 0.1 | 5 |
| G314A | — | — | — | — | — | — | |||
| Y315A | 10.1 ± 1.3 | 0.055 ± 0.009 | 5 | +8.7 ± 1.8 | 22.9 ± 0.5 | 5 | −62.8 ± 1.1 | 5.5 ± 0.1 | 5 |
| T316A | 5.4 ± 1.0 | 0.006 ± 0.006 | 5 | +11.7 ± 2.3 | 22.9 ± 0.8 | 5 | −72.2 ± 0.6 | 6.8 ± 0.3 | 5 |
| L317A | 5.1 ± 0.7 | 0.066 ± 0.007 | 5 | +21.6 ± 1.2 | 23.9 ± 0.2 | 5 | −72.6 ± 0.9 | 7.6 ± 0.4 | 5 |
| K318A | 5.4 ± 0.5 | 0.030 ± 0.004 | 5 | +15.2 ± 0.5 | 24.1 ± 0.2 | 5 | −67.7 ± 0.4 | 5.4 ± 0.2 | 5 |
| S319A | 0.23 ± 0.03 | 0.390 ± 0.060 | 3 | — | — | — | — | ||
| C320A | 5.3 ± 0.7 | 0.033 ± 0.007 | 5 | +21.1 ± 0.9 | 24.5 ± 0.6 | 5 | −65.9 ± 1.2 | 5.0 ± 0.2 | 5 |
| C320S | 12.9 ± 1.8 | 0.309 ± 0.017 | 7 | +7.2 ± 1.7 | 31.2 ± 0.3 | 7 | −67.4 ± 1.3 | 4.9 ± 0.2 | 6 |
| A321V | 5.2 ± 0.6 | 0.178 ± 0.016 | 5 | −9.2 ± 1.1 | 21.1 ± 0.7 | 5 | −68.4 ± 0.7 | 5.0 ± 0.3 | 5 |
| S322A | 7.8 ± 2.3 | 0.042 ± 0.008 | 5 | +20.7 ± 1.9 | 20.2 ± 0.2 | 5 | −52.7 ± 2.1 | 5.8 ± 0.2 | 5 |
| E323A | 4.3 ± 0.3 | 0.000 ± 0.000 | 8 | −2.6 ± 0.4 | 19.2 ± 0.3 | 8 | −79.1 ± 0.5 | 6.8 ± 0.1 | 8 |
| L324A | 0.16 ± 0.03 | 0.693 ± 0.092 | 4 | — | — | — | — | ||
| G325A | 11.2 ± 1.3 | 0.046 ± 0.005 | 5 | +8.4 ± 1.7 | 20.4 ± 0.4 | 5 | −64.9 ± 0.9 | 6.3 ± 0.2 | 6 |
| F326A | 2.3 ± 0.3 | 0.111 ± 0.018 | 5 | +10.4 ± 4.9 | 21.0 ± 0.3 | 5 | −45.9 ± 3.0 | 6.9 ± 0.1 | 5 |
| L327A | — | — | — | — | — | — | |||
| L328A | 0.15 ± 0.01 | 0.477 ± 0.029 | 3 | — | — | — | — | ||
| F329A | — | — | — | — | — | — | |||
| V397A | 0.9 | 0.286 | 1 | +130 | 106 | 1 | — | — | |
| I398A | — | — | — | — | — | — | |||
| A399V | 0.2/0.2 | 0.23/0.22 | 2 | — | — | — | — | ||
| L400A | 1.3 ± 0.1 | 0.036 ± 0.036 | 4 | +2.9 ± 4.4 | 30.2 ± 2.1 | 4 | −92.1 ± 1.9 | 10.9 ± 0.4 | 5 |
| P401A | 0.4 ± 0.1 | 0.400 ± 0.176 | 4 | — | — | — | — | ||
| V402A | 2.4 ± 0.1 | 0.059 ± 0.007 | 5 | +0.9 ± 1.6 | 23.4 ± 0.6 | 5 | −59.2 ± 0.9 | 9.8 ± 0.2 | 5 |
| P403A | — | — | — | — | — | — | |||
| V404A | 4.8 ± 0.5 | 0.070 ± 0.026 | 4 | +13.6 ± 7.5 | 25.0 ± 2.3 | 4 | −95.2 ± 2.5 | 10.2 ± 2.5 | 6 |
| V402I:V404I | 18.4 ± 1.2 | 0.360 ± 0.015 | 6 | +10.8 ± 1.2 | 28.0 ± 0.5 | 6 | −54.4 ± 0.3 | 5.3 ± 0.2 | 6 |
| I405A | — | — | — | — | — | — | |||
| V406A | — | — | — | — | — | — | |||
| S407A | 9.6 ± 0.1 | 0.031 ± 0.004 | 9 | +7.6 ± 2.5 | 21.1 ± 0.5 | 9 | −61.0 ± 0.8 | 5.9 ± 0.4 | 6 |
| N408A | 2.7 ± 0.7 | 0.013 ± 0.008 | 5 | +28.9 ± 5.5 | 22.9 ± 1.5 | 5 | −56.2 ± 2.5 | 5.7 ± 0.3 | 5 |
| F409A | 0.5/0.4 | 0.020/0.170 | 2 | — | — | — | — | ||
| S410A | 4.1 ± 0.6 | 0.029 ± 0.010 | 5 | +12.7 ± 1.8 | 22.1 ± 0.5 | 5 | −65.3 ± 1.3 | 6.3 ± 0.2 | 5 |
| R411A | 5.3 ± 0.3 | 0.027 ± 0.010 | 5 | +8.5 ± 1.4 | 21.7 ± 2.2 | 5 | −63.2 ± 1.2 | 6.5 ± 0.7 | 8 |
| I412A | 4.4 ± 0.7 | 0.025 ± 0.003 | 6 | +8.5 ± 1.8 | 23.5 ± 0.4 | 6 | −80.2 ± 0.9 | 5.9 ± 0.2 | 9 |
| Y413A | 5.0 ± 1.7 | 0.089 ± 0.057 | 6 | +9.5 ± 0.8 | 22.0 ± 0.6 | 6 | −62.6 ± 1.2 | 7.0 ± 0.4 | 8 |
| E323A:V404A | 2.8 ± 0.2 | 0.042 ± 0.021 | 5 | +11.4 ± 3.2 | 25.3 ± 0.9 | 5 | −94.8 ± 4.5 | 7.1 ± 0.3 | 5 |
| E323A:S407A | 3.9 ± 0.6 | 0.060 ± 0.014 | 5 | +16.3 ± 2.5 | 24.1 ± 0.4 | 5 | −69.4 ± 0.9 | 6.3 ± 0.2 | 6 |
| E323A:N408A | 4.0 ± 0.3 | 0.006 ± 0.003 | 5 | +26.1 ± 2.2 | 26.4 ± 0.4 | 5 | −72.0 ± 0.7 | 6.3 ± 0.1 | 6 |
| E323A:I412A | 5.4 ± 0.7 | 0.000 ± 0.000 | 5 | +8.5 ± 2.3 | 25.0 ± 0.2 | 5 | −85.0 ± 0.8 | 6.9 ± 0.2 | 5 |
| S322A:V404A | 9.4 ± 1.2 | 0.115 ± 0.003 | 5 | +14.3 ± 1.3 | 25.5 ± 0.3 | 5 | −89.6 ± 0.5 | 5.2 ± 0.1 | 5 |
| S322A:S407A | 13.2 ± 0.4 | 0.116 ± 0.003 | 5 | +17.3 ± 0.3 | 21.5 ± 0.2 | 5 | −51.1 ± 0.4 | 5.4 ± 0.1 | 5 |
| S322A:N408A | 2.8 ± 0.4 | 0.046 ± 0.026 | 3 | +33.7 ± 2.3 | 22.3 ± 0.8 | 3 | −52.8 ± 1.1 | 5.9 ± 0.3 | 5 |
| S322A:I412A | 8.2 ± 1.2 | 0.019 ± 0.009 | 4 | +13.4 ± 1.6 | 20.7 ± 0.5 | 4 | −69.6 ± 1.4 | 6.6 ± 0.5 | 5 |
| I | V1/2,act (mV) | n | V1/2,inact (mV) | ||||||
| wt | 3.8 ± 0.6 | 0.042 ± 0.005 | 7 | +7.5 ± 0.7 | 20.4 ± 0.7 | 7 | −66.9 ± 0.8 | 5.9 ± 0.3 | 9 |
| G309A | 11.5 ± 1.1 | 0.425 ± 0.020 | 5 | −1.7 ± 1.1 | 22.3 ± 0.1 | 5 | −74.7 ± 0.9 | 5.2 ± 0.2 | 5 |
| L310A | 1.4 ± 0.3 | 0.148 ± 0.025 | 9 | +131 ± 19 | 62.0 ± 7.3 | 4 | −19.7 ± 0.4 | 12.1 ± 0.6 | 3 |
| R311A | 3.9 ± 0.6 | 0.020 ± 0.011 | 5 | +26.1 ± 2.3 | 22.9 ± 0.8 | 5 | −48.2 ± 2.1 | 5.8 ± 0.1 | 5 |
| I312A | 13.9 ± 1.7 | 0.224 ± 0.018 | 5 | +13.8 ± 2.0 | 20.7 ± 0.3 | 5 | −72.3 ± 1.1 | 7.7 ± 0.4 | 5 |
| L313A | 3.3 ± 0.4 | 0.011 ± 0.007 | 5 | +12.0 ± 0.3 | 25.0 ± 0.2 | 5 | −77.5 ± 0.4 | 7.0 ± 0.1 | 5 |
| G314A | — | — | — | — | — | — | |||
| Y315A | 10.1 ± 1.3 | 0.055 ± 0.009 | 5 | +8.7 ± 1.8 | 22.9 ± 0.5 | 5 | −62.8 ± 1.1 | 5.5 ± 0.1 | 5 |
| T316A | 5.4 ± 1.0 | 0.006 ± 0.006 | 5 | +11.7 ± 2.3 | 22.9 ± 0.8 | 5 | −72.2 ± 0.6 | 6.8 ± 0.3 | 5 |
| L317A | 5.1 ± 0.7 | 0.066 ± 0.007 | 5 | +21.6 ± 1.2 | 23.9 ± 0.2 | 5 | −72.6 ± 0.9 | 7.6 ± 0.4 | 5 |
| K318A | 5.4 ± 0.5 | 0.030 ± 0.004 | 5 | +15.2 ± 0.5 | 24.1 ± 0.2 | 5 | −67.7 ± 0.4 | 5.4 ± 0.2 | 5 |
| S319A | 0.23 ± 0.03 | 0.390 ± 0.060 | 3 | — | — | — | — | ||
| C320A | 5.3 ± 0.7 | 0.033 ± 0.007 | 5 | +21.1 ± 0.9 | 24.5 ± 0.6 | 5 | −65.9 ± 1.2 | 5.0 ± 0.2 | 5 |
| 12.9 ± 1.8 | 0.309 ± 0.017 | 7 | +7.2 ± 1.7 | 31.2 ± 0.3 | 7 | −67.4 ± 1.3 | 4.9 ± 0.2 | 6 | |
| A321V | 5.2 ± 0.6 | 0.178 ± 0.016 | 5 | −9.2 ± 1.1 | 21.1 ± 0.7 | 5 | −68.4 ± 0.7 | 5.0 ± 0.3 | 5 |
| S322A | 7.8 ± 2.3 | 0.042 ± 0.008 | 5 | +20.7 ± 1.9 | 20.2 ± 0.2 | 5 | −52.7 ± 2.1 | 5.8 ± 0.2 | 5 |
| E323A | 4.3 ± 0.3 | 0.000 ± 0.000 | 8 | −2.6 ± 0.4 | 19.2 ± 0.3 | 8 | −79.1 ± 0.5 | 6.8 ± 0.1 | 8 |
| L324A | 0.16 ± 0.03 | 0.693 ± 0.092 | 4 | — | — | — | — | ||
| G325A | 11.2 ± 1.3 | 0.046 ± 0.005 | 5 | +8.4 ± 1.7 | 20.4 ± 0.4 | 5 | −64.9 ± 0.9 | 6.3 ± 0.2 | 6 |
| F326A | 2.3 ± 0.3 | 0.111 ± 0.018 | 5 | +10.4 ± 4.9 | 21.0 ± 0.3 | 5 | −45.9 ± 3.0 | 6.9 ± 0.1 | 5 |
| L327A | — | — | — | — | — | — | |||
| L328A | 0.15 ± 0.01 | 0.477 ± 0.029 | 3 | — | — | — | — | ||
| F329A | — | — | — | — | — | — | |||
| V397A | 0.9 | 0.286 | 1 | +130 | 106 | 1 | — | — | |
| I398A | — | — | — | — | — | — | |||
| A399V | 0.2/0.2 | 0.23/0.22 | 2 | — | — | — | — | ||
| L400A | 1.3 ± 0.1 | 0.036 ± 0.036 | 4 | +2.9 ± 4.4 | 30.2 ± 2.1 | 4 | −92.1 ± 1.9 | 10.9 ± 0.4 | 5 |
| P401A | 0.4 ± 0.1 | 0.400 ± 0.176 | 4 | — | — | — | — | ||
| V402A | 2.4 ± 0.1 | 0.059 ± 0.007 | 5 | +0.9 ± 1.6 | 23.4 ± 0.6 | 5 | −59.2 ± 0.9 | 9.8 ± 0.2 | 5 |
| P403A | — | — | — | — | — | — | |||
| V404A | 4.8 ± 0.5 | 0.070 ± 0.026 | 4 | +13.6 ± 7.5 | 25.0 ± 2.3 | 4 | −95.2 ± 2.5 | 10.2 ± 2.5 | 6 |
| 18.4 ± 1.2 | 0.360 ± 0.015 | 6 | +10.8 ± 1.2 | 28.0 ± 0.5 | 6 | −54.4 ± 0.3 | 5.3 ± 0.2 | 6 | |
| I405A | — | — | — | — | — | — | |||
| V406A | — | — | — | — | — | — | |||
| S407A | 9.6 ± 0.1 | 0.031 ± 0.004 | 9 | +7.6 ± 2.5 | 21.1 ± 0.5 | 9 | −61.0 ± 0.8 | 5.9 ± 0.4 | 6 |
| N408A | 2.7 ± 0.7 | 0.013 ± 0.008 | 5 | +28.9 ± 5.5 | 22.9 ± 1.5 | 5 | −56.2 ± 2.5 | 5.7 ± 0.3 | 5 |
| F409A | 0.5/0.4 | 0.020/0.170 | 2 | — | — | — | — | ||
| S410A | 4.1 ± 0.6 | 0.029 ± 0.010 | 5 | +12.7 ± 1.8 | 22.1 ± 0.5 | 5 | −65.3 ± 1.3 | 6.3 ± 0.2 | 5 |
| R411A | 5.3 ± 0.3 | 0.027 ± 0.010 | 5 | +8.5 ± 1.4 | 21.7 ± 2.2 | 5 | −63.2 ± 1.2 | 6.5 ± 0.7 | 8 |
| I412A | 4.4 ± 0.7 | 0.025 ± 0.003 | 6 | +8.5 ± 1.8 | 23.5 ± 0.4 | 6 | −80.2 ± 0.9 | 5.9 ± 0.2 | 9 |
| Y413A | 5.0 ± 1.7 | 0.089 ± 0.057 | 6 | +9.5 ± 0.8 | 22.0 ± 0.6 | 6 | −62.6 ± 1.2 | 7.0 ± 0.4 | 8 |
| E323A:V404A | 2.8 ± 0.2 | 0.042 ± 0.021 | 5 | +11.4 ± 3.2 | 25.3 ± 0.9 | 5 | −94.8 ± 4.5 | 7.1 ± 0.3 | 5 |
| E323A:S407A | 3.9 ± 0.6 | 0.060 ± 0.014 | 5 | +16.3 ± 2.5 | 24.1 ± 0.4 | 5 | −69.4 ± 0.9 | 6.3 ± 0.2 | 6 |
| E323A:N408A | 4.0 ± 0.3 | 0.006 ± 0.003 | 5 | +26.1 ± 2.2 | 26.4 ± 0.4 | 5 | −72.0 ± 0.7 | 6.3 ± 0.1 | 6 |
| E323A:I412A | 5.4 ± 0.7 | 0.000 ± 0.000 | 5 | +8.5 ± 2.3 | 25.0 ± 0.2 | 5 | −85.0 ± 0.8 | 6.9 ± 0.2 | 5 |
| S322A:V404A | 9.4 ± 1.2 | 0.115 ± 0.003 | 5 | +14.3 ± 1.3 | 25.5 ± 0.3 | 5 | −89.6 ± 0.5 | 5.2 ± 0.1 | 5 |
| S322A:S407A | 13.2 ± 0.4 | 0.116 ± 0.003 | 5 | +17.3 ± 0.3 | 21.5 ± 0.2 | 5 | −51.1 ± 0.4 | 5.4 ± 0.1 | 5 |
| S322A:N408A | 2.8 ± 0.4 | 0.046 ± 0.026 | 3 | +33.7 ± 2.3 | 22.3 ± 0.8 | 3 | −52.8 ± 1.1 | 5.9 ± 0.3 | 5 |
| S322A:I412A | 8.2 ± 1.2 | 0.019 ± 0.009 | 4 | +13.4 ± 1.6 | 20.7 ± 0.5 | 4 | −69.6 ± 1.4 | 6.6 ± 0.5 | 5 |
Peak current amplitudes at +40 mV (IP,+40) and the relative current remaining after 1.5 s (f+40) were measured for Kv4.2 wild-type (wt), single mutant, and double mutant channels. The mutations G314A, L327A, F329A, I398A, P403A, I405A, and V406A produced channels with currents indistinguishable from endogenous voltage-dependent oocyte conductances. From peak conductance–voltage relationships and steady-state inactivation curves, the voltages for half-maximal activation (V1/2,act) and inactivation (V1/2,inact), respectively, and the corresponding slope factors s were determined with Boltzmann analysis. Some mutants with poor expression and/or extreme voltage shift, including S319A, L324A, L328A, V397A, A399V, P401A, and F409A, were not further analyzed.
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