Which of the following statements is true about the G-protein-coupled receptor (GPCR)?
G protein can be either stimulatory (Gs) or inhibitory (Gi). Stimulatory or inhibitory activity resides in the a subunit. G-protein coupled receptor (GPCR) are cell membrane receptors that span the membrane 7 times hennce called seven helix or serpentine receptors. Upon ligand binding to GPCR, a conformational change activates the G protein (present inside the cell). Heterotrimeric G protein (3 subunits a,b,g. Couple the cell surface receptor (GPCR) to catalytic units that catalyse the intracellular formation of second messenger F. In resting-state a subunit is bound to GDP. The intrinsic GTPase activity of the subunit then conves GTP to GDP, and this leads to reassociation of the a with the b-g subunit and termination of effector activation. Ref: Guyton and Hall 13th edition Pgno: 931
G protein bind the hormones on the surface of the nucleus
All the three subunits a, b and g should bind to each other for G protein to act
G protein act as inhibitory and excitatory because of difference in a subunit
G protein is bound to GTP in resting state
General physiology