A, B, C, D, and E are, respectively, typical K+ currents elicited by the voltage protocol inset in C (not to scale), for Shaker-IR-WT, Shaker-IR-L409A, Shaker-IR-S411A, Shaker-IR-S412A, and Shaker-IR-F433A channels. (F) Weighted inactivation time constants calculated from a double exponential fit to currents from WT, L409A, S411A, S412A, and F433A channels. (G) Fraction of the fast component of inactivation for channels tested as indicated in the graph. (H, I, J, K, and L) are, respectively, charge-voltage (Q-V) (open square), conductance-voltage (G-V) (solid circle), and Inac-voltage (Inac-V) curves (solid diamond) for WT (black), L409A (green), S411A (blue), S412A (light purple), and F433A (orange) channels. Currents used to build Inac-V curves were taken from the peak currents elicited by the 60 mV testing pulse after the 19 s inactivating period. M, N, and O are, respectively, shifts (from WT values) in the energy involved in the second component of Q-V, G-V, and Inact-V curves, as caused by L409A, S411A, S412A, and F433A mutations. Continuous lines over G-V, Q-V, and Inac-V curves are the best fits to Equations 2, 3, and 7, respectively. Q-V from F433A:W434F was fitted using Equation 4. The best-fitted values are listed in Table 1. Data shown as mean ± SEM for F to L; and mean ± SE for M to O (N=5-8).