title: The forgotten serine. A critical role for Ser-2035.42 in ligand binding to and activation of the beta 2-adrenergic receptor.
abstract: Previous work in the beta(2)-adrenergic receptor demonstrated critical interactions between Ser-204 and Ser-207 in the fifth membrane-spanning segment and the meta-OH and para-OH, respectively, of catecholamine agonists (Strader, C. D., Candelore, M. R., Hill, W. S., Sigal, I. S., and Dixon, R. A. (1989) J. Biol. Chem. 264, 13572-13578). Using the substituted cysteine accessibility method in the beta(2)-adrenergic receptor, we have found that in addition to Ser-204 and Ser-207, Ser-203 is also accessible on the surface of the binding-site crevice and is occluded by bound agonist. Mutation of Ser-203 to Ala, Val, or Cys reduced the binding affinity and adenylyl cyclase-activating potency of agonists containing a meta-OH, whereas their affinities and potencies were largely preserved by mutation of Ser-203 to Thr, which maintained an OH at this position. Thus both Ser-203 and Ser-204 appear to interact with the meta-OH of catecholamines, perhaps through a bifurcated H bond. Furthermore, the removal of the OH at position 203 led to a significant loss of affinity of antagonists with nitrogen in their heterocyclic ring structure. The greatest effect was seen with pindolol, a partial agonist, suggesting that a H bond between the heterocyclic ring and Ser-203 may play a role in partial agonism. In contrast, the affinities of antagonists such as propranolol or alprenolol, which have cyclic structures without H-bonding capability, were unaltered after mutation of Ser-203.
authors.affiliation: Center for Molecular Recognition and the Departments of Psychiatry and Pharmacology, Columbia University College of Physicians and Surgeons and the New York State Psychiatric Institute, New York, New York 10032,USA.
authors.forename: G
authors.initials: G
authors.lastname: Liapakis
authors.forename: J A
authors.initials: JA
authors.lastname: Ballesteros
authors.forename: S
authors.initials: S
authors.lastname: Papachristou
authors.forename: W C
authors.initials: WC
authors.lastname: Chan
authors.forename: X
authors.initials: X
authors.lastname: Chen
authors.forename: J A
authors.initials: JA
authors.lastname: Javitch
mesh_terms: D058672:Adrenergic beta-2 Receptor Antagonists; D000595:Amino Acid Sequence; D000818:Animals; D002460:Cell Line; D006801:Humans; D006860:Hydrogen Bonding; D008024:Ligands; D011485:Protein Binding; D018343:Receptors, Adrenergic, beta-2 / Q000737:chemistry / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D012694:Serine / Q000378:metabolism*; D013816:Thermodynamics
chemical_list: D058672:Adrenergic beta-2 Receptor Antagonists; D008024:Ligands; D018343:Receptors, Adrenergic, beta-2; D012694:Serine