Table 4. The influence of upper interface single-, double- and triple-mutations on slow inactivation gating of the tandem dimer Shaker Kv channela .
| Channel protein | Onset of inactivation time constant (τo) (msec) | Steady-state inactivation amplitude (Ass) | Forwards inactivation time constant (τf) (msec) | Backwards inactivation time constant (τr) (msec) | Equilibrium constant for inactivation gate closure (K I)b | ΔG inactivation c (kcal/mol) | ΔΔG inactivation e (kcal/mol) | Recovery from inactivation time constant (τrecovery) d (msec) |
| Wild type (AWTBWT) | 11950±248 | 0.27±0.01 | 16460±836 | 43613±1420 | 2.65±0.10 | −0.57±0.03 | 0 | 3728±108 |
| T248A (AWTBT248A) | 7957±255 | 0.20±0.02 | 9981±1336 | 39676±3416 | 3.97±0.40 | −0.81±0.09 | 0.24±0.095 | 3353±254 |
| Y415A (AY415ABWT) | 6093±137 | 0.22±0.01 | 7841±484 | 27321±1107 | 3.48±0.16 | −0.73±0.04 | 0.16±0.05 | 5444±172 |
| S428A (AS428ABWT) | 9469±138 | 0.31±0.04 | 13811±2348 | 30117±2909 | 2.18±0.30 | −0.46±0.11 | −0.11±0.11 | 3082±48 |
| T248A;Y415A (AY415ABT248A) | 2311±278 | 0.17±0.01 | 2801±354 | 13205±1483 | 4.71±0.27 | −0.91±0.09 | 0.34±0.095 | 6434±669 |
| T248A;S428A (AS428ABT248A) | 2385±114 | 0.19±0.02 | 2937±429 | 12686±1233 | 4.32±0.47 | −0.86±0.10 | 0.29±0.1 | 2580±84 |
| Y415A;S428A (AY415A;S428ABWT) | 3950±65 | 0.26±0.03 | 5381±803 | 14849±1321 | 2.75±0.33 | −0.60±0.10 | 0.03±0.1 | 3229±94 |
| Y415A;S428A;T248A (AY415A;S428ABT248A) | 900±25 | 0.18±0.02 | 1101±161 | 4918±464 | 4.46±0.50 | −0.88±0.10 | 0.31±0.1 | 9645±577 |
K I) and the free energy for inactivation gate closure (ΔG inactivation), for all single-, double- and triple-mutants used to calculate the coupling free energies during inactivation gating.a The table displays the forward and backward time constants for slow inactivation gating (at 0 mV) along with the inactivation equilibrium constant (
K I were calculated according to K I = k f/k r (see Materials and Methods).b Values for
ΔG inactivation were calculated according to ΔG inactivation = −RTln K I.c Values for
Materials and Methods).d Values for the slow recovery phase are presented (see
ΔΔG inactivation were calculated according to ΔΔG inactivation = (−RTln (k f/k b)wt −−RTln (k f/k b)m).e Values for