Figure 6.

AGS3 stabilizes Gα_i3 in its inactive GDP-bound form. Activation of Gα_i3 by AlF₄⁻ is visualized by a dramatic enhancement of the fluorescence of Gα_i3 tryptophans. The amplitude of activation of Gα_i3 is significantly decreased in the presence of AGS3_424–650. Gα_i3-GDP was preincubated in the absence or presence of AGS3_424–650 before addition of NaF (arrow 1) and AlCl₃ (arrow 2). Tryptophan fluorescence was monitored by spectrofluorometry as described in Materials and Methods. Time is expressed in seconds and fluorescence in arbitrary units.