Isolation and N-terminal amino acid sequence of an octopamine ligand binding protein

An octopamine receptor photoaffinity probe was used to label membranes from the light organs of Photinus pyralis, a tissue highly enriched in octopamine receptors. Labeling was concentrated in a glycoprotein of 75 +/- 2 kDa with lesser labeling of a 79 +/- 2 kDa component. Labeling could be displaced by prior incubation with octopamine, mianserin, cyproheptadine, phentolamine or propranolol, with a relative potency that correlated with the ability of these same agents to modulate light organ octopamine-sensitive adenylate cyclase. The 75 kDa binding protein was isolated and its N-terminal amino acid sequence was determined.