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目的:研究受体第三细胞内环(IL_3)的长度对受体与配基结合及与G蛋白偶联特性的影响.方法:用目前已知的G蛋白偶联受体中IL_3最短的血管紧张素Ⅱ AT_1受体的IL_3替换野生型D_2受体较长的IL_3,组成D_2/AT,嵌合受体.结果:与野生型D_2受体相比,D_2/AT_1嵌合受体与拮抗剂的亲和性均降低,与激动剂的亲和性有的增高,有的降低.嵌合受体失去与G蛋白偶联的能力,也不能产生磷酸肌醇水解.结论:受体的IL_3对受体配基结合位点和空间构象有一定影响;受体与G蛋白的偶联不仅与IL_3有关,而且还受非IL_3区域的影响,而IL_3的长度是决定这两方面影响的因素之一.
OBJECTIVE: To study the effect of the length of the third intracellular loop (IL_3) on the binding of receptor to ligand and the binding of G protein.Methods: With the currently known G protein-coupled receptors, the shortest IL_3 IL_3 of AT_1 receptor of angiotensin Ⅱ replaced the longer IL_3 of wild type D_2 receptor and formed D_2 / AT chimeric receptor.Results: Compared with wild type D_2 receptor, D_2 / AT_1 chimeric receptor and antagonist Affinity of agonists decreased, some decreased, chimeric receptors lost the ability to couple with G protein, and did not produce phosphoinositide hydrolysis.Conclusion: IL_3 Receptor ligand binding site and spatial conformation have some impact; receptor and G protein coupling not only with IL_3, but also by the impact of non-IL_3 region, and the length of IL_3 is to determine one of the two factors .