The classical model of G-protein signaling suggests that the G-protein dissociates upon GPCR activation. The active alpha subunit then participates in signaling, until its intrinsic GTPase activity degrades the bound GTP to GDP. The inactive G alpha (12/13):GDP complex has much higher affinity for the G beta:gamma complex and consequently reassociates into the inactive heterotrimeric G-protein.
Siderovski, DP, Willard, FS
Oldham, WM, Hamm, HE
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