TABLE 4
Affinities of Gs- and Gi-proteins for TNP-ATP and TNP-GTP High-affinity GTPase activity in Sf9 membranes expressing various GPCR-Gα fusion proteins was determined as described under Materials and Methods in the presence of Mg2+. Reaction mixtures contained TNP-nucleotides at concentrations from 1 nM to 100 μM as appropriate to generate saturated inhibition curves. Inhibition curves were analyzed by nonlinear regression and were best-fitted to monophasic sigmoidal curves. Ki values were calculated from IC50 values using the previously determined Km values (Gille and Seifert, 2003b). Data shown are the means ± S.D. of three experiments performed in duplicates.