FIGURE 7.

Effects of MTSET modification at 164C are blocker-dependent. A, blockade of the Kir6.2[L164C] dimer was examined in the presence of 10 μm PG-11098, a synthetic spermine analog, before and after modification by MTSET. B, schematic illustrating potential interpretation, with blockers longer than spermine extending closer toward the positive charge introduced at position 164C. SH indicates the sulfhydryl group of the cysteint (L164C) available for modification in half of the subunits. C, conductance-voltage relationships before (n = 7) and after (n = 7) MTSET modification illustrate a rightward shift and smaller effective valence of PG-11098 block after MTSET. Error bars indicate S.E. D, kinetics of PG-11098 unbinding before (left panel) and after (right panel) MTSET modification. Patches were pulsed to +50 mV, in control (gray) or 10 μm PG-11098 (black), and repolarized to −50 mV to observe blocker unbinding. Prepulses to +90 mV were also used to ensure significant channel block by PG-11098 after MTSET modification, although PG-11098 unbinding remained rapid.