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首页> 外文期刊>Molecular and Cellular Biology >The C Terminus of the Saccharomyces cerevisiaeα-Factor Receptor Contributes to the Formation of Preactivation Complexes with Its Cognate G Protein
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The C Terminus of the Saccharomyces cerevisiaeα-Factor Receptor Contributes to the Formation of Preactivation Complexes with Its Cognate G Protein

机译：酿酒酵母α因子受体的C总站有助于与其相关的G蛋白的预激活复合物的形成。

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Binding of the α-factor pheromone to its G-protein-coupled receptor (encoded by STE2) activates the mating pathway inMATa yeast cells. To investigate whether specific interactions between the receptor and the G protein occur prior to ligand binding, we analyzed dominant-negative mutant receptors that compete with wild-type receptors for G proteins, and we analyzed the ability of receptors to suppress the constitutive signaling activity of mutant Gα subunits in an α-factor-independent manner. Although the amino acid substitution L236H in the third intracellular loop of the receptor impairs G-protein activation, this substitution had no influence on the ability of the dominant-negative receptors to sequester G proteins or on the ability of receptors to suppress theGPA1-A345T mutant Gα subunit. In contrast, removal of the cytoplasmic C-terminal domain of the receptor eliminated both of these activities even though the C-terminal domain is unnecessary for G-protein activation. Moreover, the α-factor-independent signaling activity of ste2-P258L mutant receptors was inhibited by the coexpression of wild-type receptors but not by coexpression of truncated receptors lacking the C-terminal domain. Deletion analysis suggested that the distal half of the C-terminal domain is critical for sequestration of G proteins. The C-terminal domain was also found to influence the affinity of the receptor for α-factor in cells lacking G proteins. These results suggest that the C-terminal cytoplasmic domain of the α-factor receptor, in addition to its role in receptor downregulation, promotes the formation of receptor–G-protein preactivation complexes.
机译：α因子信息素与其G蛋白偶联受体（由 STE2 编码）的结合激活了 MAT 酵母细胞中的交配途径。为了调查受体和G蛋白之间是否发生特定的相互作用，然后才与配体结合，我们分析了与野生型受体竞争G蛋白的显性负突变受体，并分析了受体抑制G组成型信号传导活性的能力。突变的Gα亚基以独立于α因子的方式存在。尽管受体第三胞内环中的氨基酸取代L236H会损害G蛋白活化，但这种取代对显性负受体螯合G蛋白的能力或受体抑制的能力均没有影响。 GPA1-A345T 突变Gα亚基。相反，除去受体的胞质C-末端结构域消除了这两种活性，即使C-末端结构域对于G蛋白活化而言是不必要的。此外，野生型受体的共表达抑制了 ste2-P258L 突变体受体的α-因子非依赖性信号传导活性，但缺少C末端结构域的截短受体的共表达没有抑制这种表达。缺失分析表明，C末端结构域的远侧半部对于螯合G蛋白至关重要。还发现C端结构域影响缺乏G蛋白的细胞中受体对α因子的亲和力。这些结果表明，α因子受体的C末端胞质域除了在受体下调中的作用外，还促进了受体G蛋白预激活复合物的形成。

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