Fig. 1.
Ligand induced activation of a G protein-coupled receptor (GPCR). GPCRs (blue) are transmembrane receptors which activate intracellular signalling pathways, through coupling to G proteins. These heterotrimeric proteins consist of three subunits denoted α, β and γ, and are classically activated by a ligand induced conformational change in the GPCR [2]. This movement is proposed to involve a rotational transmembrane helix reorientation, exposing an intracellular binding cleft [3]. GDP is exchanged for GTP on Gα, while the βγ complex splits away and is able to signal independently of the Gα subunit. Humans encode 18, 5 and 12 different α, β and γ subunits, respectively. These combine into a variety of stimulatory (Gs) or inhibitory (Gi/q) effects on pathways including those dependent on adenylyl cyclase and phospholipase C. Created with Biorender.com.