The beta2-adrenergic receptor (beta2AR) is a well-studied prototype for heterotrimeric guanine nucleotide-binding protein (G protein)-coupled receptors (GPCRs) that respond to diffusible hormones and neurotransmitters. To overcome the structural flexibility of the beta2AR and to facilitate its crystallization, we engineered a beta2AR fusion protein in which T4 lysozyme (T4L) replaces most of the third intracellular loop of the GPCR ("beta2AR-T4L") and showed that this protein retains near-native pharmacologic properties. Analysis of adrenergic receptor ligand-binding mutants within the context of the reported high-resolution structure of beta2AR-T4L provides insights into inverse-agonist binding and the structural changes required to accommodate catecholamine agonists. Amino acids known to regulate receptor function are linked through packing interactions and a network of hydrogen bonds, suggesting a conformational pathway from the ligand-binding pocket to regions that interact with G proteins.
Science (new York, N.y.), 2007, Vol 318, Issue 5854, p. 1266-73
Adrenergic beta-Agonists; Adrenergic beta-Antagonists; Amino Acid Sequence; Bacteriophage T4; Binding Sites; Cell Line; Cell Membrane; Crystallization; Crystallography, X-Ray; Drug Inverse Agonism; Humans; Immunoglobulin Fab Fragments; Ligands; Models, Molecular; Molecular Sequence Data; Muramidase; Propanolamines; Protein Conformation; Protein Structure, Secondary; Protein Structure, Tertiary; Receptors, Adrenergic, beta-2; Recombinant Fusion Proteins