Amino acid residues involved in the interaction with the intrinsic agonist (R)-octopamine in the β-adrenergic-like octopamine receptor from the silkworm Bombyx mori

Octopamine (OA) is a biogenic amine that controls a variety of important physiological processes and behaviors of invertebrates. To identify the amino acid residues interacting with (R)-OA in a beta-adrenergic-like OA receptor from the silkworm Bombyx mori (BmOAR2), the wild-type receptor and seven mutant receptors with an amino acid substitution at a potential orthosteric site were expressed in HEK-293 cells and examined for their ability to elevate intracellular cAMP levels ([cAMP](i)) in response to (R)-OA. The S206A mutant receptor retained the ability to increase [cAMP](i) after (R)-OA treatment. In contrast, the other six mutant receptors (D115A, S202A, Y300F, Y300N, Y300L, and Y300A) lacked the ability to elevate [cAMP](i). These results indicate that Asp115, Ser202, and Tyr300 participate in (R)-OA binding and the activation of BmOAR2. Homology modeling studies suggest that Ser202 and Tyr300 interact with the phenolic OH group of (R)-OA, whereas Asp 115 interacts with the beta-OH group and the NH(2) group of (R)-OA. (C) Pesticide Science Society of Japan