Fig. 3.

Receptor-mediated G protein activation schematic. A. Gα protein (Gβγ not shown), with specific elements in the GTPase domain labeled. GDP is held in the cleft between the GTPase and helical domains. B. Receptor activation impinges on the C-terminal α5 helix, and interactions of IC2 with secondary sites such as the αN/β1 hinge and α4/β6 loop dynamically alter interactions at the base of the α5 helix with surrounding regions. C. Receptor-mediated G protein activation results in the nucleotide-free, empty pocket state of the Gα protein, and a conformationally dynamic helical domain.