# G Protein-Coupled Receptors (GPCRs) **G Protein-Coupled Receptors (GPCRs)** are a large family of receptors that contain seven transmembrane $\alpha$ helices. **GCPRs** - Ligand binding activates the receptor, which activates the G protein, which activates an effector enzyme to generate an intracellular second messenger. - All GPCRs contain 7 membrane spanning regions with their N-terminus on the exoplasmic face and C-terminus on the cytosolic face ## Types of GPCRs ### Trimeric GPCRs GTP-binding proteins (or G proteins) ![[Pasted image 20250312045305.png|383]] ## Inhibitors ## Signal Termination Signaling is terminated by GTP hydrolysis (aka G alpha inactivation), receptor phosphorylation by G protein-coupled receptor kinases (GRKs), beta-arrestin binding (aka desensitization), and receptor internalization or degradation. The binding of arrestin to the phosphorylated GPCRs allows for internalization