Positioning of a single LE mutant subunit in a concatenated hERG1 tetramer does not affect biophysical properties or response to PD. (A) Representative current traces for LE₁/WT₃ and WT₃/LE₁ hERG1 channels. Pulses were applied to V_t of −70 to 30 mV in 20-mV increments. V_h was −80 mV and V_ret was −70 mV. (B) Normalized I_tail-V_t relationships before and after 10 µM PD. Symbol legend is the same as for C. For LE₁/WT₃ hERG1 channels: V_0.5act = −32.1 ± 1.3 mV, z = 4.13 ± 0.14 mV (control); V_0.5act = −30.1 ± 1.6 mV, z = 4.20 ± 0.07 mV (PD; n = 11). For WT₃/LE₁ hERG1 channels: V_0.5act = −29.1 ± 1.5 mV, z = 3.36 ± 0.21 mV (control); V_0.5act = −27.1 ± 1.3 mV, z = 3.44 ± 0.16 mV (PD; n = 4). (C) Normalized fully activated I_tail-V_ret relationships determined before and after 10 µM PD. (D) [PD]-response relationships for LE₁/WT₃ hERG1 channels (EC₅₀ = 4.6 µM, n_H = 1.1; n = 6–9) and WT₃/LE₁ hERG channels (EC₅₀ = 4.8 µM, n_H = 1.4; n = 4). Data are expressed as mean ± SEM (n = number of oocytes).