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- Title
Molecular mechanisms of ligand-receptor interactions in transmembrane domain V of the α[sub2A]-adrenocepter.
- Authors
Peltonen, Juha M.; Nyronen, Tommi; Wurster, Siegfried; Pihlavisto, Marjo; Hoffren, Anna-Marja; Marjamaki, Anne; Xhaard, Henri; Kanerva, Liisa; Savola, Juha-Matti; Johnson, Mark S.; Scheinin, Mika
- Abstract
1 The structural determinants of catechol hydroxyl interactions with adrenergic receptors were examined using 12 α[sub2]-adrenergic agonists and a panel of mutated human α[sub2A]-adrenoceptors. The α[sub2A]Ser201 mutant had a Cys→Ser201 (position 5.43) amino-acid substitution, and α[sub2A]Scr201Cys200 and α[sub2A]Ser201Cys204 had Ser→Cys200 (5.42) and Ser →Cys204 (5.46) substitutions, respectively, in addition to the Cys→Ser201 substitution. 2 Automated docking methods were used to predict the receptor interactions of the ligands. Radioligand-binding assays and functional [[sub35]GTPγS-binding assays were performed using transfected Chinese hamster ovary cells to experimentally corroborate the predicted binding modes. 3 The hydroxyl groups of phenethylamines were found to have different effects on ligand affinity towards the activated and resting forms of the wild-type α[sub2A]-adrenoceptor. Substitution of Ser200 or Ser204 with cysteine caused a deterioration in the capability of catecholamines to activate the &alpha[sub2A];-adrenoceptor. The findings indicate that (i) Cys20l plays a significant role in the binding of catecholamine ligands and UK 14.304 (for the latter. by a hydrophobic interaction), but Cys20l is not essential for receptor activation: (ii) Ser200 interacts with the meta-hydroxyl group of phenethylamine ligands, affecting both catecholamine binding and receptor activation; while (iii) substituting Ser204 with a cysteine interferes both with the binding of catecholamine ligands and with receptor activation, due to an interaction between Ser204 and the para-hydroxyl group of the calecholic ring.
- Subjects
ALPHA adrenoceptors; RECEPTOR-ligand complexes; MOLECULAR biology; CATECHOLAMINES; LIGAND binding (Biochemistry); G proteins
- Publication
British Journal of Pharmacology, 2003, Vol 140, Issue 2, p347
- ISSN
0007-1188
- Publication type
Article
- DOI
10.1038/sj.bjp.0705439