The GTPase activity of WT, E244G, and E244G, Q951G. The assay for GTPase activity is identical to the one used to measure ATP hydrolysis except that 16 μg of plasma membrane protein was used in each reaction GTPase activity of WT (■), E244G (▲), and E244G, Q951G (▼) were compared. Plots are the average of three independent experiments from three independent plasma membrane vesicle preparations of each strain (n=3).