Figure 3.

Inhibition of activity of different AC forms by βγ subunits of heterotrimeric G proteins. (A) AC activity in either membranes of Sf9 cells expressing the full-length ACI or in mixtures of subdomains from ACI and ACV was stimulated with G_sα*. The G_sα* concentrations used were identical to those in Fig. 2A. The effect of various concentrations of βγ subunits to modulate AC activity was monitored. Data are presented as percent inhibition of G_sα*-stimulated activity and are the mean ± SEM (n = 3 experiments). (B) Same as A except that the AC activity was stimulated by addition of CaM (500 nM). Ca²⁺ was present at a final concentration of 30 μM. Percent inhibition of Ca²⁺/CaM-stimulated activity is shown as the mean ± SEM (n = 3 experiments).