Final answer:
G proteins inactivate themselves by hydrolyzing bound GTP to GDP, which ensures precise regulation of cell signaling by acting as a 'built-in' off-switch. This self-regulation prevents overstimulation and maintains the cyclic nature of cell signaling processes.
Step-by-step explanation:
G proteins, once activated by binding with GTP (guanosine triphosphate), have an intrinsic GTPase activity enabling them to hydrolyze the GTP back to GDP (guanosine diphosphate). This hydrolysis prompts the inactivation of these proteins. This self-regulatory mechanism happens after the activated G protein has triggered a series of downstream signals, which typically involve either activation or inhibition of target proteins like adenylate cyclase, leading to the generation of second messengers such as cAMP (cyclic AMP).
The hydrolysis of GTP to GDP is critical because it ensures that the signal transduction is a tightly regulated process, occurring only when appropriate and for a suitable amount of time. This 'built-in' off-switch prevents overstimulation and potential cell damage due to prolonged pathway activation. Thus, the cycle of activation and inactivation of G proteins allows for the precise control of cell signaling pathways.
Once GTP is hydrolyzed, the G-protein subunits reassociate into an inactive state, ready to be activated once again by another signaling event. This cyclical nature of G-protein function is key to the dynamic regulation of cellular activities, facilitating response to various extracellular signals.