PIP₂ inhibits activation in Elk1 Δ2–136 and K5Q mutants. (A) τ_act(10 µM PIP₂)/τ_act(Ctrl) at various voltages compared for WT (n = 18) and Δ2–136 (n = 9). Accurate measurement of the Δ2–136 activation time constant below −10 mV was not possible in 1-s steps because of the depolarized G-V. The inset compares normalized currents for a Δ2–136 patch at 10 mV on cell, excised, and in the presence of 10 µM PIP₂. (B) Repeat of A for K5Q (n = 8). (C) ΔV₅₀ induced by 10 µM PIP₂ in excised patches for WT, Δ2–136, and K5Q (n = 37, 14, and 8, respectively; ***, P < 0.001 vs. WT; t test).