Figure 8.

Effects of mutations in the WA motif of SUR1 on Mg-nucleotide activation. (A and B) Concentration-activation relationships for MgADP (A) or MgATP (B) for channels composed of Kir6.2-G334D and SUR1 (open circles; n = 6), SUR1-KAKA (closed circles; n = 5), SUR1-K1A (closed squares; n = 5), or SUR1-K2A (open squares; n = 5) channels. The solid lines are the best fit of Eq. 3 to the mean data (A, open circles: a = 0.84, EC₅₀ = 9 µM, h = 1.3; B, open circles: a = 0.88, EC₅₀ = 124 µM, h = 1.3; closed squares: a = 0.52, EC₅₀ = 150 µM, h = 1.3; open squares: a = 0.40, EC₅₀ = 200 µM, h = 1.1; closed circles: a = 0.05, EC₅₀ = 150 µM, h = 1.3) except for data for channels containing mutant SUR1 subunits in A, where the lines are drawn by hand. The dotted lines indicate the relationship obtained for Kir6.2-G334D/SUR1 in the presence of 30 µM gliclazide (shown in Fig. 7). Mean ± SEM.