Agonists induce conformational changes in transmembrane domains III and VI of the beta(2) adrenoceptor
Agonists induce conformational changes in transmembrane domains III and VI of the beta(2) adrenoceptor
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DOI：
10.1093/emboj/16.22.6737
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发表时间：
1997-11-17
期刊：
影响因子：
11.4
通讯作者：
Kobilka, BK
中科院分区：
文献类型：
--
作者：
Gether, U;Lin, S;Kobilka, BK
激动剂与G蛋白偶联受体的结合被认为促进构象变化，导致活性受体状态的形成。然而，提供激动剂结合和G蛋白偶联之间的重要联系的这种构象变化的特征尚不清楚，在这里，我们报告的证据表明，激动剂结合β（2）肾上腺素受体诱导构象变化周围的（125）半胱氨酸跨膜结构域（TM）纯化了一系列具有有限数量的可用于化学衍生化的半胱氨酸的突变体β（2）肾上腺素受体，用构象敏感的半胱氨酸反应性荧光团IANBD进行位点选择性标记，并通过荧光光谱法进行分析。含有（125）Cys和/或（285）Cys的突变受体显示激动剂诱导的荧光降低，而在这两个半胱氨酸突变的受体中没有观察到激动剂诱导的应答，这些数据表明，与（125）Cys和（285）Cys结合的IANBD在激动剂结合后暴露于更极性的环境，并表明跨膜区段III和VI的运动参与G蛋白偶联受体的活化。
Agonist binding to G protein-coupled receptors is believed to promote a conformational change that leads to the formation of the active receptor state, However, the character of this conformational change which provides the important link between agonist binding and G protein coupling is not known, Here we report evidence that agonist binding to the beta(2) adrenoceptor induces a conformational change around (125)Cys in transmembrane domain (TM) III and around (285)Cys in TM VI, A series of mutant beta(2) adrenoceptors with a limited number of cysteines available for chemical derivatization were purified, site-selectively labeled with the conformationally sensitive, cysteine-reactive fluorophore IANBD and analyzed by fluorescence spectroscopy, Like the wild-type receptor, mutant receptors containing (125)Cys and/or (285)Cys showed an agonist-induced decrease in fluorescence, while no agonist-induced response was observed in a receptor where these two cysteines were mutated, These data suggest that IANBD bound to (125)Cys and (285)Cys are exposed to a more polar environment upon agonist binding, and indicate that movements of transmembrane segments III and VI are involved in activation of G protein-coupled receptors.