Agonist binding and activation of the rat β1-adrenergic receptor: Role of Trp134 (3.28), Ser190 (4.57) and Tyr356 (7.43)

Abstract

We investigated the role of Trp134 (3.28), Ser 190 (4.57) and Tyr356 (7.43) in agonist binding to, and activation of, the rat β1-adrenergic receptor by comparing pKis and functional responses of W134A, S190A and Y356F mutant receptors to wild type, all stably expressed in CHO cells. All three mutations significantly (P < 0.05) reduced adenylyl cyclase intrinsic activity (IA) compared to wild type in response to stimulation with both (-)-isoprenaline (53-88%) and (-)-RO363 (46-61%), and there was no significant correlation either between IA or pD2 and pKi (P > 0.4), suggesting that changes in pKi were not sufficient to explain the fall in adenylyl cyclase activity. The most pronounced reducti..