Figure 6
Conserved gating properties in zebrafish Kv3.3 channels. A) Wild type zebrafish Kv3.3 currents were evoked by pulsing from -90 mV to voltages ranging from -80 to +60 mV in 10 mV increments. The bath contained 4 mM K+. The -10 mV trace is labeled for comparison to Fig. 10A. The traces were obtained using the kcnc3a WIKP splice variant (see Fig. 4D). B) Normalized amplitudes of isochronal tail currents have been plotted versus voltage. Tail currents were recorded in an 89 mM Rb+ bath solution. The membrane was pulsed from -90 to +60 mV for 15 ms prior to repolarization to -90 mV. Data were fitted with a single Boltzmann function to obtain values for the midpoint voltage (V1/2) and slope factor, which were -13.8 ± 0.3 mV and 6.6 ± 0.1 mV, respectively (n = 5). Black squares, kcnc3a WIKP splice variant; blue circles: kcnc3a PSIL splice variant (see Fig. 4D). C) Currents were evoked by pulsing from -90 mV to +20 mV. Black trace: kcnc3a WIKP variant; blue trace: kcnc3a PSIL variant (see Fig. 4D). Traces were scaled to the same amplitude and overlaid. D) The N-terminal extension of Kv3.3 between the first and second methionine residues was removed by mutating the initial ATG. Current traces were evoked by pulsing from -90 mV to voltages ranging from -80 to +60 mV in 10 mV increments. Currents are shown on a compressed time scale. The traces were obtained using the kcnc3a WIKP splice variant (see Fig. 4D).