Figure 5.
A, The broad-spectrum protein kinase inhibitor H8 blocked the more negatively activating component of K+ current. Perforated-patch currents from a P15 type I hair cell. External application of 15 μm H8 reversibly blocked the conductance at the holding potential, gHP of −69 mV (arrows). The H8-sensitive (Control, H8) traces at large depolarizations crossed over those at smaller depolarizations, a pattern typical of erg channels (see C and Results). B, Activation curves from tail currents show that the H8-sensitive conductance was the most negative part of the total conductance and turned over at higher voltages, as seen in erg activation curves. V1/2, S, and gmax values from single Boltzmann fits: Control, −65 mV, 7.6 mV, 49 nS; H8, −51 mV, 7.7 mV, 35 nS; H8-sensitive, −70 mV, 5.9 mV, 28 nS. C, K+ current from a different type I cell; control solutions. The current evoked by a voltage command to +73 mV (black current and voltage traces) inactivates and crosses over current traces at lower depolarizations (gray traces), resembling erg currents.