FIGURE 6.
Competitive equilibrium binding of SK and SKΔK414 to [5F]FFR-Pm and FFR-Pm in the presence of benzamidine. A, the fractional change in fluorescence (ΔF/Fo) of 2.5 nm [5F]FFR-Pm in buffer containing 50 mm benzamidine plotted as a function of the total SK concentration ([SK]o) in the absence (•) and presence of 5.15 (○) and 15 nm (•) FFR-Pm. B, the fractional change in fluorescence (ΔF/Fo) of 5 nm [5F]FFR-Pm in buffer containing 50 mm benzamidine plotted as a function of the total SKΔK414 concentration ([SKΔK414]o) in the absence (•) and presence of 10 nm (○) FFR-Pm. The solid lines represent least-squares fits of the cubic equation for competitive binding, with the parameters listed under “Results” and Table 1. Fluorescence titrations were performed and analyzed as described under “Experimental Procedures.”