Fig. 3.

GPCR-G protein/arrestin complexes. a Crystal structure of arrestin 1 (PDB 1CF1) showing the membrane-anchoring c-loop. b Solvent-accessible surface. Hydrophobic surface (red); Hydrophilic surface (white). c Biased signaling of serotonin 5-HT2B receptors. Activated 5-HT2B receptor (PDB 7SRQ) is preferentially coupled to Gαs protein (PDB 7SRR). The receptor could also couple to β-arrestin 1 (PDB 7SRS). Gαs and β-arrestin 1 engaged on the same cavity formed by the cytoplasmic receptor interface