Final answer:
Signaling by the G-alpha subunit of a G-protein-coupled receptor is terminated through the hydrolysis of GTP to GDP. This leads to the inactivation of the G-alpha subunit and re-association with the beta and gamma subunits, resetting the system for the next signal.
Step-by-step explanation:
Mechanism of G-alpha Subunit Signaling Termination
The signaling by the G-alpha subunit is terminated through a process known as hydrolysis. When a signaling molecule binds to a G-protein-coupled receptor, a GDP molecule associated with the G-alpha subunit is exchanged for GTP. Following this, the beta and gamma subunits dissociate from the G-alpha subunit, which triggers a cellular response. The signal is then terminated by the hydrolysis of GTP back to GDP, which inactivates the G-alpha subunit. Once GDP is bound, the alpha subunit re-associates with the beta and gamma subunits forming the inactive G-protein, resetting the complex for the next signal.
This mechanism is crucial for regulating cell signaling and ensuring that the response does not persist longer than necessary. The cycle of activation and deactivation of G-proteins is essential for maintaining homeostasis within cells and ensuring appropriate responses to extracellular signals.