N1–135 coexpression has no effect on channels that have a CNBD deletion but does modify gating in distal C-terminal region–deleted channels. (A, C, and E) Channel schematics and two-electrode voltage-clamp recordings of a family of currents from hERG ΔN Δdistal C + N1–135 (A), hERG ΔN ΔCNBD/distal C + N1–135 (C), and hERG ΔN ΔCNBD + N1–135 (E). Currents were elicited using the pulse protocols indicated. Insets showing tail currents at −50 mV are 200 ms in duration; inset scale bars are 0.5 μA. (B, D, and F) Two-electrode voltage-clamp recordings of a family of tail currents from the constructs in A, C, and E. Currents were elicited using the pulse protocol indicated. (G) Normalized I-V relationship for A, C, and E. n ≥ 5 for each. (H) Normalized G-V relationship for A, C, and E. Data were fit with a Boltzmann function to determine the V_1/2 and k (slope) values. n ≥ 6 for each. (I) Plot of the time to half-maximal activation for A, C, and E. n ≥ 5 for each. (J) Plot of the time constants (τ) of deactivation derived from a single exponential fit to the tail currents in B, D, and F. n ≥ 5 for each. For G–J, the values are plotted as the means ± SEM. The error bars are within the points if not visible. hERG (closed squares) and hERG ΔN (open squares) are included on all plots for reference.