Figure 4.

Saturation of the rate of agonist-stimulated, GRPr-catalyzed GDP/GTPγS exchange by Gα_q and Gβγ. (A) The concentrations of GRP (1 μM), GRPr (0.4 nM), and βγ (1.2 μM) were fixed, and the concentration of Gα_q varied from 28 nM to 426 nM as indicated. (B) The concentration of GRP (1 μM), GRPr (3 nM), and Gα_q (284 nM) were fixed, and the concentration of βγ was varied from 34 nM to 1200 nM. Binding reactions proceeded for 15 min at 30°C, and the binding was determined as described.