Fig. 6. Mutational effects of the SUR1 subunit on the G_βγ2-dependent modulation of K_ATP channels. (A) Single channel currents were recorded continuously from COS-7 cells co-expressed with wild-type Kir6.2 subunit together with the mutant SUR1 subunit, S1LM1. (a) Control (in the absence of ATP); (b) in the presence of 100 µM ATP or (c) 100 µM ATP plus 50 pM G_βγ2; and (d) after wash-out of G_βγ2 or (e) G_βγ2 plus ATP. Arrowheads, the zero current levels. (B) Current responses (NP_o) to 100 µM ATP were measured in the absence (open boxes) or presence (filled boxes) of 50 pM G_βγ2 in the wild-type or mutant channels as indicated, and expressed as a ratio to those in the absence of ATP. The number of experiments is indicated in parentheses. **P<0.001. NS, not significant.