Vol. 56, Issue 5, 909-916, November 1999

Study of Interaction between Agonists and Asn293 in Helix VI of Human ₂-Adrenergic Receptor

Helene M. Zuurmond, Jutta Hessling, Klaus Blüml, Martin Lohse, and Adriaan P. Ijzerman

Leiden/Amsterdam Center for Drug Research, Division of Medicinal Chemistry, Leiden, the Netherlands (H.M.Z., A.P.IJ.); and University of Würzburg, Institute of Pharmacology and Toxicology, Würzburg, Germany (J.H., K.B., M.L.)

Previously, we demonstrated the involvement of Asn293 in helix VI of the human ₂-adrenergic receptor in stereoselective agonist recognition and activation. In the present study, we have further explored the role of this residue by synthesizing derivatives of isoproterenol and clenbuterol, two -adrenergic receptor agonists. We analyzed their efficacy and affinity on the wild-type and a mutant receptor (Asn293Leu). Each compound had similar efficacy ( values) on both the wild-type and mutant receptor, although  values varied considerably among the eight compounds studied. It appeared that one derivative of isoproterenol, but not of clenbuterol, showed a gain in affinity from the wild type to the mutant receptor. This derivative had a methyl substituent instead of the usual -OH group in the aliphatic side chain of isoproterenol, compatible with the more lipophilic nature of the leucine side chain. Such a "gain of function" approach through a combination of synthetic chemistry with molecular biology, may be useful to enhance our insight into the precise atomic events that govern ligand-receptor interactions.