Fig. 1.

G protein coupled receptor-mediated activation of signal transduction pathway: Membrane-bound GPCR is associated with Gα, Gβ and Gγ proteins where Gα protein is bound with GDP which is functionally inactive form. In the presence of extracellular ligand, GDP is replaced by GTP and both Gα and Gβγ protein heterodimer relocate along the membrane to associate with the specific ion channels and activate intracellular signalling pathways. In the presence of modulator, the Gα activates the GTPase activity and hydrolyses the GTP and the pocket is occupied by the GDP which is coupled with the release of ligand from GPCR