Fig. 2. (A ) [35S]GTPγS binding of recombinant Gαi1. Data are the mean of three measurements. Open circles = control data;solid line = control data fit with y = a (1 − e−kt);closed circle = amount of [35S]GTPγS bound by Gαi1in the presence of 10 μm suramin;filled triangles = amount of [35S]GTPγS bound by Gαi1in the presence of 1 mm halothane. The ordinate is the amount of Gαi1bound to [35S]GTPγS relative to the amount of [35S]GTPγS bound after 3 h. (B ) GTPγS binding of recombinant Gαi1assayed by the intrinsic fluorescence increase. Each curve is the average of three measurements. Solid line = intrinsic fluorescence increase of the control;dotted line = curve in the presence of 0.6 mm halothane;dashed line = curve in the presence of 10 μm suramin. The fluorescence curves were fit with the equation y = a (1 − e−kt) and scaled by the a parameter of the fit to the control [35S]GTPγS binding time course to place them on the same ordinate scale. GTP = guanosine 5′-triphosphate.