English: Animation showing the hypothesized conformational changes of the G protein throughout the G protein cycle. The GDP-bound heterotrimer (gray) binds to activated receptor (blue), and the nucleotide-binding pocket region consisting of β6-α5, the P-loop and switch 2 are perturbation, resulting in GDP (purple) release. Subsequently, the helical domain of Gα(GDP) opens away from the receptor-anchored Ras domain, which allows GDP release and GTP (orange) to enter. Reorientation of Gα caused by GTP binding leads to dissociation of the receptor and Gβγ (Gβ; green and Gγ; cyan). GTP hydrolysis leads to rebinding of Gβγ to Gα in order to restart the G protein signaling cycle.