Figure 8: Y545 Split HERG channels retain properties residing in the permeation module.
(a) Inhibition of split HERG currents by E-4031. The time course of current inhibition in response to an addition of 100 μM E-4031 is shown on the left. Currents were elicited in response to 1 s depolarizing pulses to +40 mV from a holding potential of −40 mV followed by a repolarization step to −50 mV. Pulses were delivered at a frequency of 0.1 Hz. Representative tail current traces before and after 5 min of treatment with E−40131 are shown on the insets. A bar histogram relating the extent of current inhibition with the concentration of the inhibitor is shown on the right. (b). Absence of functional expression upon co-injection of cRNAs encoding N-terminal 1–545 and non-conducting C-terminal 546–1,159 KV11.1 demi-channels carrying a G628S point mutation in the pore. Currents were obtained in 50 mM extracellular K+ using the voltage protocol shown at the top. Families of currents from non-mutant (left) and G628S (right) splits are shown. (c) Characterization of voltage-dependent currents elicited by co-expression of KV11.1 demi-channels carrying a S620T point mutation in the pore domain. The voltage protocol used to elicit the currents is shown at the top. Representative families of currents recorded in response to the protocol are shown in the insets. Top panels, I versus V relationships from normalized currents measured in 2 mM (open squares, left) and 50 mM (closed circles, right) extracellular K+ at the end of the depolarization step. Lower panel, current/voltage relationship generated using peak tail currents measured in 2 mM extracellular K+ (open circles). Data from normally inactivating non-mutated split channels obtained in the same conditions are shown as dashed lines (Y545 Split) for comparison. Error bars represent s.e.
