title: The docking of Arg2 of angiotensin II with Asp281 of AT1 receptor is essential for full agonism.
abstract: The structural model of AT1 angiotensin receptor contains seven-transmembrane alpha-helices with three interhelical loops on either side of the membrane. The angiotensin II binding pocket within the receptor is not clearly defined. We showed earlier that Lys199 in transmembrane-helix-5 of the AT1 receptor binds the COOH-terminal alpha-carboxyl group of angiotensin II (Noda, K., Saad, Y., Kinoshita, A., Boyle, T. P., Graham, R. M., Husain, A., and Karnik, S. S. (1995) J. Biol. Chem. 270, 2284-2289). We now show that His183 and Asp281, both located in the extracellular domain of the AT1 receptor, are involved in binding the NH2-terminal Asp1 and Arg2 residues of angiotensin II, respectively. The Asp1/His183 interaction appears to be weak and is unlikely to be important for agonism. But the loss of Arg2/Asp281 interaction leads to partial agonism of the receptor. The action of non-peptide agonists is not affected by Asp281 mutations. These results suggest that several independent interactions between angiotensin II and AT1 receptor are necessary for full agonism. Since L-162,313 the non-peptide agonist of the AT1 receptor is a partial agonist that does not make contact with Asp281, we speculate that the degree of agonism may be increased if it is redesigned to make contacts with Asp281.
authors.affiliation: Department of Molecular Cardiology, Cleveland Clinic Foundation, Ohio 44195-5069, USA.
authors.forename: Y H
authors.initials: YH
authors.lastname: Feng
authors.forename: K
authors.initials: K
authors.lastname: Noda
authors.forename: Y
authors.initials: Y
authors.lastname: Saad
authors.forename: X P
authors.initials: XP
authors.lastname: Liu
authors.forename: A
authors.initials: A
authors.lastname: Husain
authors.forename: S S
authors.initials: SS
authors.lastname: Karnik
mesh_terms: D000804:Angiotensin II / Q000031:analogs & derivatives / Q000037:antagonists & inhibitors / Q000378:metabolism*; D057911:Angiotensin Receptor Antagonists; D001120:Arginine / Q000378:metabolism; D001224:Aspartic Acid / Q000378:metabolism; D001665:Binding Sites; D001713:Biphenyl Compounds / Q000494:pharmacology; D007093:Imidazoles / Q000494:pharmacology; D007295:Inositol Phosphates / Q000378:metabolism; D019808:Losartan; D008958:Models, Molecular; D011485:Protein Binding; D011945:Receptors, Angiotensin / Q000819:agonists* / Q000145:classification / Q000378:metabolism*; D013329:Structure-Activity Relationship; D013777:Tetrazoles / Q000494:pharmacology
chemical_list: D057911:Angiotensin Receptor Antagonists; D001713:Biphenyl Compounds; D007093:Imidazoles; D007295:Inositol Phosphates; D011945:Receptors, Angiotensin; D013777:Tetrazoles; D000804:Angiotensin II; D001224:Aspartic Acid; C009210:sarleucin; D001120:Arginine; D019808:Losartan