FIGURE 4.

The Kir2.1(E272G) also accelerates the gating kinetics albeit to a smaller extent than V223L. A, The RMSF of Kir2.1 and E272G in the GH loop, the linker between the CD and G-loops. The mutant causes an increase in RMSF relative to the control. B, dose-responses of diC8 PIP₂ on Kir2.1 and the E272G mutant reveal a small leftward shift in apparent affinity caused by the mutation. C, peak currents of Kir2.1 and the E272G mutant appear comparable. D, the representative time course of current inhibition (PIP₂ dephosphorylation induced by Ci-VSP, a 1.8-fold effect) of WT-Kir2.1 and E272G. E, the representative time course of reactivation (PIP₂ rephosphorylation, a 2.2-fold effect comparable with the inhibitory effect shown in D) of WT-Kir2.1 and E272G. F, summary bars (left and right) represent the time constants (mean ± S.E. of at least six experiments) corresponding to D and E, respectively.