Figure 1.

κ-PVIIA blocks Shaker currents differently in symmetrical K⁺ and Rb⁺. (Left) Current responses to voltage steps from a holding potential of −100 mV to −20 and +60 mV, under control conditions and with 200 nM κ-PVIIA in symmetrical K⁺ (top) and 500 nM κ-PVIIA in symmetrical Rb⁺ (bottom). (Middle) Current in toxin is scaled to the control to evidence the effect of the toxin. Note that besides a reduction in the current amplitude, also a modification in the kinetics of the current is observed. (Right) Ratio between the toxin and control current traces. The dotted lines correspond to the tonic unblock for closed state, respectively 0.58 in K⁺ and 0.37 in Rb⁺, corresponding to a K^C of 265 nM and 293 nM, respectively. The single exponential fits are superimposed to the traces: in symmetrical K⁺ (top) at +60 mV, τ = 9.56 ms and U = 0.76; at −20 mV, τ = 27.2 ms and U = 0.26. In symmetrical Rb⁺ (bottom) at +60 mV, τ = 4.6 ms and U = 0.87; at −20 mV, τ = 5.65 ms and U = 0.60.