Figure 1. Different ligand-stabilized GPCR conformations cause binding and activation of distinct signal transducers including G proteins and arrestins.

(Left) Crystal structure of β₂AR (light blue cartoon) coupled to Gαs (blue) Gβ (orange) Gγ (green) heterotrimer (PDB ID: 3SN6 (Rasmussen et al., 2011b)) illustrates G protein-mediated signaling. Upon heterotrimer activation, subunits dissociate and Gα modulates second messenger production such as cAMP production through Gαs-mediated activation of adenylyl cyclase. Gβγ modulates separate Gα-independent downstream signaling networks such as ion channels, phospholipases, and receptor kinases.

(Right) Crystal structure of rhodopsin (light blue cartoon) coupled to β-arrestin (salmon) (PDB ID: 4ZWJ (Kang et al., 2015)) illustrates arrestin mediated effects such as receptor internalization or activation of kinase signaling networks.