2. G Protein–Coupled Receptors and Second Messengers

The β-Adrenergic Receptor System Acts through the Second Messenger cAMP

Cyclic AMP Activates Protein Kinase A

BOX 12-1 FRET: Biochemistry in a Living Cell

Several Mechanisms Cause Termination of the β-Adrenergic Response

The β-Adrenergic Receptor Is Desensitized by Phosphorylation and by Association with Arrestin

Cyclic AMP Acts as a Second Messenger for Many Regulatory Molecules

G Proteins Act as Self-Limiting Switches in Many Processes

BOX 12-2 Receptor Guanylyl Cyclases, cGMP, and Protein Kinase G

Diacylglycerol, Inositol Trisphosphate, and Ca2+ Have Related Roles as Second Messengers

Calcium Is a Second Messenger That Is Limited in Space and Time