Ser203 as well as Ser204 and Ser207 in fifth transmembrane domain of the human beta2-adrenoceptor contributes to agonist binding and receptor activation.
We examined the contribution of Ser203 of the human beta2-adrenoceptor (beta2-AR) to the interaction with isoprenaline. The affinity of (-)-isoprenaline was reduced by substitution of an alanine for Ser203, as well as for Ser204 and Ser207. An (-)-isoprenaline derivative with only one hydroxyl group, at the meta-position, showed reduced affinity for wild-type beta2-AR and S207A-beta2-AR and even lower affinities for S203A-beta2-AR and S204A-beta2-AR. By contrast, an (-)-isoprenaline derivative with only a para-hydroxyl group showed reduced affinity for wild-type beta2-AR but the serine to alanine mutations did not cause further decreases. The EC50 value for cyclic AMP generation in response to (-)-isoprenaline was increased, by about 120 fold, for each alanine-substituted beta2-AR mutant. These results suggest that Ser203 of the human beta2-AR is important for both ligand binding and receptor activation.
Sato
T
T
Laboratory of Pharmacology and Toxicology, Graduate School of Pharmaceutical Sciences, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
Kobayashi
H
H
Nagao
T
T
Kurose
H
H
D000316:Adrenergic alpha-Agonists / Q000378:metabolism* / Q000494:pharmacology*; D000409:Alanine / Q000378:metabolism; D019943:Amino Acid Substitution / Q000235:genetics / Q000502:physiology; D000818:Animals; D016466:CHO Cells; D006224:Cricetinae; D006801:Humans; D007545:Isoproterenol / Q000031:analogs & derivatives / Q000494:pharmacology; D007700:Kinetics; D009154:Mutation; D051381:Rats; D018341:Receptors, Adrenergic, alpha-2 / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D012694:Serine / Q000378:metabolism*
D000316:Adrenergic alpha-Agonists; D018341:Receptors, Adrenergic, alpha-2; D012694:Serine; D007545:Isoproterenol; D000409:Alanine