FIGURE 2.
MgADP-induced conformational switching of SURs. The solid lines are fits to a logistic equation: IC50 values: WT: 161 ± 28, slope = 1.7 ± 0.4; Q1178R: 25 ± 2, slope = 1.5 ± 0.1. Values are means ± S.E., n > 10. Dashed lines are drawn through the data points for SUR1E1507D and SUR1E1507Q. The apparent affinity for this receptor is difficult to estimate. Its affinity for MgADP is lower than WT, whereas its affinity for MgATP is significantly higher, and thus a significant fraction of the switching above 300 μm ADP may reflect the conversion of ADP to ATP by endogenous adenylate kinase in the membrane preparations.