Final answer:
GTP binding proteins, also known as G proteins, are membrane-localized proteins that play a crucial role in cell signaling. They are activated by binding to G-protein-coupled receptors and activate downstream signaling events. To turn off the signaling, the GTP on the active alpha subunit is hydrolyzed to GDP.
Step-by-step explanation:
GTP binding proteins, also known as G proteins, are a group of membrane-localized proteins that play a crucial role in cell signaling. They are activated by binding to G-protein-coupled receptors (GPCRs) in response to a ligand. When the G-protein binds to the receptor, it undergoes a conformational change and exchanges GDP for GTP. This activates the G-protein, and its subunits split into alpha (α) and beta-gamma (βγ) subunits.
The activation of GTP-bound alpha subunit (Gα-GTP) triggers downstream signaling events, while the beta-gamma subunit (βγ) can also participate in signaling or interact with other effector molecules.
To turn off the G-protein signaling, the GTP on the active alpha subunit is hydrolyzed to GDP. This deactivates the alpha subunit, and the alpha and beta-gamma subunits reassociate to form the inactive G-protein complex, ready for another cycle of signaling.