Pollock N J, Manelli A M, Hutchins C W, Steffey M E, MacKenzie R G, Frail D E
Department of Corporate Molecular Biology, Abbott Laboratories, Abbott Park, Illinois 60064.
J Biol Chem. 1992 Sep 5;267(25):17780-6.
Several serines present in transmembrane domain V are conserved among members of the G-protein-coupled receptor family that bind catecholamines. Two of these serines that are present in the beta-adrenergic receptor were previously shown by site-directed mutagenesis to affect agonist binding and receptor activation (Strader, C. D., Candelore, M. R., Hill, W. S., Sigal, I. S., and Dixon, R. A. F. (1989) J. Biol. Chem. 264, 13572-13578). We investigated the role of the serines present in transmembrane V of another catecholamine receptor, the dopamine D1 receptor, by site-directed mutagenesis, and the results show that mutations at serines 198, 199, and 202 affect dopamine binding. The substitution of serine 198 or serine 199 by an alanine also affects the binding of several other agonist and antagonist dopaminergic compounds while an alanine substitution at serine 202 has no effect on the binding of these compounds. Moreover, each single serine mutation decreased the maximal cAMP accumulation elicited by a dopamine D1 partial agonist. These results suggest that serines present in transmembrane V of the D1 receptor affect ligand interactions and receptor signal transduction, but not entirely in the manner that would be predicted from the model proposed for the beta-adrenergic receptor.
跨膜结构域V中存在的几个丝氨酸在结合儿茶酚胺的G蛋白偶联受体家族成员中是保守的。β-肾上腺素能受体中存在的其中两个丝氨酸先前已通过定点诱变表明会影响激动剂结合和受体激活（斯特拉德，C.D.，坎德洛雷，M.R.，希尔，W.S.，西加尔，I.S.，以及迪克森，R.A.F.（1989年）《生物化学杂志》264卷，第13572 - 13578页）。我们通过定点诱变研究了另一种儿茶酚胺受体——多巴胺D1受体跨膜V区中丝氨酸的作用，结果表明丝氨酸198、199和202处的突变会影响多巴胺结合。用丙氨酸取代丝氨酸198或丝氨酸199也会影响其他几种激动剂和拮抗剂多巴胺能化合物的结合，而丝氨酸202处用丙氨酸取代对这些化合物的结合没有影响。此外，每个单个丝氨酸突变都会降低多巴胺D1部分激动剂引发的最大环磷酸腺苷积累。这些结果表明，D1受体跨膜V区中的丝氨酸会影响配体相互作用和受体信号转导，但并不完全按照为β-肾上腺素能受体提出的模型所预测的方式。
