Site-directed mutagenesis of the rat beta1-adrenoceptor. Involvement of Tyr356 (7.43) in (+/-)cyanopindolol but not (+/-)[125Iodo]cyanopindolol binding.
To determine the role played by Tyr(356 (7.43)) in the rat beta(1)-adrenoceptor in binding the antagonists (+/-)cyanopindolol (4-[3-(t-butylamino]-3-(2'-cyano-indoloxy)-2-propanolol) and its iodinated analogue (+/-)[(125)Iodo]cyanopindolol (1-(t-butylamino]-3-(2'-cyano-3'-iodo-indoloxy)-2-propanolol), Tyr(356 (7.43)) was mutated to either Phe or Ala and binding affinities determined for wild type and mutant rat beta(1)-adrenoceptors. Our results indicate that Tyr(356 (7.43)) is important for (+/-)cyanopindolol, but not (+/-)[(125)Iodo]cyanopindolol, binding and that (+/-)cyanopindolol adopts a "reverse" binding orientation whereas (+/-)[(125)Iodo]cyanopindolol cannot be accommodated in this binding mode. We define a "reverse" antagonist binding mode as one where the aryloxy moiety interacts with residues on transmembrane helices 1, 2, 3 and 7. The beta(1)-adrenoceptor site-directed mutagenesis results are the first to support a "reverse" antagonist binding orientation and the involvement of Tyr(356 (7.43)) in this binding mode.
Rezmann-Vitti
Linda A
LA
Clinical Pharmacology and Therapeutics Unit, Department of Medicine, The University of Melbourne, Austin Health, Heidelberg, 3084 Victoria, Australia.
Louis
Simon N S
SN
Nero
Tracy L
TL
Jackman
Graham P
GP
Machida
Curtis A
CA
Louis
William J
WJ
D000319:Adrenergic beta-Antagonists / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology; D000818:Animals; D007457:Iodine Radioisotopes; D008958:Models, Molecular; D016297:Mutagenesis, Site-Directed; D010869:Pindolol / Q000031:analogs & derivatives* / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology; D011485:Protein Binding; D011487:Protein Conformation; D011869:Radioligand Assay; D051381:Rats; D018342:Receptors, Adrenergic, beta-1 / Q000235:genetics / Q000378:metabolism*; D014443:Tyrosine / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
D000319:Adrenergic beta-Antagonists; D007457:Iodine Radioisotopes; D018342:Receptors, Adrenergic, beta-1; D014443:Tyrosine; C047975:cyanopindolol; D010869:Pindolol