Figure 2.

Half-channel chimeras between rNa_V1.4 and hNa_V1.5/rNa_V1.8. (A) Topological cartoon of a Na_Vα-subunit with four homologous domains (DI–DIV). Boundaries used for the construction of domain chimeras (red diamonds) and pore loop chimeras are indicated. Residue numbers refer to rNa_V1.4. (B, D) Superposition of current traces at −20 mV before (black) and after application of 1 µM µ-CnIIIC (red) for chimeras 4455 and 5544 in HEK 293 cells (B), as well as traces at 10 mV for 4*488 and 8844 in Neuro-2A cells with 10 µM µ-CnIIIC (D). (C, E) Mean remaining current (left) and apparent time constant of onset of block for the indicated chimeras. Vertical lines indicate the mean values of the respective wild-type channels. ‘n.b.’ refers to a situation where no onset was measured because channels were not blocked. The n values are shown in parentheses. Note that chimera 4*488 carries the additional mutation Y401S in order to make this construct resistant to TTX. In the background of rNa_V1.4, this mutation does not strongly alter the ability of 1 µM µ-CnIIIC to block the channel (89.5 ± 0.4% block for Y401S, n= 6).