Action of the alpha subunit of G-protein is:
The α-subunit has GTPase activity: the bound GTP is slowly hydrolysed to GDP: the α-subunit then dissociates from the effector to rejoin its other subunits, but not before the effector has been activated / inhibited for several seconds (much longer than the life-time of the activated receptor, which is in milliseconds) and the signal has been greatly amplified. The rate of GTP hydrolysis by the α subunit and thus the period for which it remains activated is regulated by another protein called ‘regulator of G protein signaling’ (RGS). The onset time of response through GPCRs is in seconds.
KEY CONCEPT:-
Alpha subunit of G protein contains GTPase which breaks GTP into GDP.
Reference: Essentials of Medical Pharmacology Eighth Edition KD TRIPATHI page no 55
Binding of antagonist
Breakdown of GTP to GDP
Conversion of GDP to GTP
All of the above