Figure 5.

AGS3 is a GDI for Gα_i3. Shown is the time course of GTPγ³⁵S binding by Gα_i3-, Gα_o-, and Gα_s-GDP in the absence or presence of AGS3_424–650. AGS3 inhibits (up to 85%) GTPγS binding to Gα_i3. The effect is observed as early as 5 min and lasts over the entire 80-min time period. No inhibition of GTPγS binding to Gα_o or Gα_s is observed in the presence of AGS3_424–650. GTPγ³⁵S was incubated in the absence or presence of 1 μM His-AGS3_424–650. Gα-GDP (50 nM final) subunits were added to start the reaction, and the reaction was stopped at different times by filtration. Results represent the mean of three (Gα_s, Gα_o) or four (Gα_i3) experiments.