Mapping of beta-adrenoceptor coupling domains to Gs-protein by site-specific synthetic peptides.

Peptides corresponding to the known sequence of turkey erythrocyte beta 1-adrenergic receptor were synthesized and the effects on receptor-mediated cyclase activation were measured. Peptides corresponding to the first and second intracellular loops (T61-71 and T138-159) inhibited at micromolar concentrations the hormone-dependent cyclase activation in turkey erythrocyte membranes. In contrast, the peptide corresponding to the C-terminal part of the third intracellular loop (T284-295) increased the cyclase activity in a hormone-independent manner. Peptides T338-353 and T2-10 and a number of synthetic peptides unrelated to the beta-adrenoceptor had no effect.