FIGURE 11.

Slow inactivation of ROMK-IRK chimeras is structure-dependent. A depolarization (V_m + 70 mV) was applied for 60 min beginning at time zero, with external [K] at 1 mM in all cases. Positive voltage produced no outward current in these strong inward rectifiers. The labels on each curve refer to the chimeras described in Fig. 1. During the two-electrode voltage clamp period with intact oocytes, internal pH was maintained at 7.04 by external acetate buffer at pHo = 7.8. Inward conductance was measured periodically using 20-ms voltage steps to generate momentary inward current during the sustained depolarization. All of the channels in this figure lack the pH sensor at K61.