Fig. 2
From: QR code model: a new possibility for GPCR phosphorylation recognition
Ligand-GPCR-GRK-arrestin information transfer process. After the ligand activates the GPCR, GRK phosphorylates the activated receptor. Arrestin recognizes the phosphorylated receptor and binds to it, thereby causing receptor desensitization, endocytosis or the continuation of signal transmission. In this process, different GRKs phosphorylate different sites on the receptor. Arrestin recognizes these differences in phosphorylation sites and binds to the receptor in different structural conformations to perform different functions. The orange shapes represent different ligands, the gray dots represent sites that are not phosphorylated, and the red dots represent sites that are phosphorylated.