BACKGROUND Stimulation of phospholipase Cβ (PLCβ) by the activated α-subunit of Gq (Gαq) constitutes a major signaling pathway for cellular regulation, and structural studies have recently revealed the molecular interactions between PLCβ and Gαq. Yet, most of the PLCβ-interacting residues identified on Gαq are not unique to members of the Gαq family. Molecular modeling predicts that the core PLCβ-interacting residues located on the switch regions of Gαq are similarly positioned in Gαz which does not stimulate PLCβ. Using wild-type and constitutively active chimeras constructed between Gαz and Gα14, a member of the Gαq family, we examined if the PLCβ-interacting residues identified in Gαq are indeed essential. RESULTS Four chimeras with the core PLCβ-interacting residues composed of Gαz sequences were capable of binding PLCβ2 and stimulating the formation of inositol trisphosphate. Surprisingly, all chimeras with a Gαz N-terminal half failed to functionally associate with PLCβ2, despite the fact that many of them contained the core PLCβ-interacting residues from Gα14. Further analyses revealed that the non-PLCβ2 interacting chimeras were capable of interacting with other effector molecules such as adenylyl cyclase and tetratricopeptide repeat 1, indicating that they could adopt a GTP-bound active conformation. CONCLUSION Collectively, our study suggests that the previously identified PLCβ-interacting residues are insufficient to ensure productive interaction of Gα14 with PLCβ, while an intact N-terminal half of Gα14 is apparently required for PLCβ interaction.

中文翻译：

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Gα14刺激磷脂酶Cβ需要完整的螺旋结构域。

背景技术Gq（Gαq）的活化α-亚基刺激磷脂酶Cβ（PLCβ）构成细胞调节的主要信号传导途径，并且结构研究最近揭示了PLCβ和Gαq之间的分子相互作用。然而，在Gαq上鉴定的大多数与PLCβ相互作用的残基并不是Gαq家族成员所独有的。分子建模预测，位于Gαq的开关区域上的核心PLCβ相互作用残基类似地位于Gαz中，这不会刺激PLCβ。我们使用在Gαq和Gαq家族成员Gα14和Gα14之间构建的野生型和组成型嵌合体，研究了在Gαq中鉴定出的与PLCβ相互作用的残基是否确实必要。结果四个嵌合的，具有与Gαz序列组成的核心PLCβ相互作用残基的嵌合体能够结合PLCβ2并刺激肌醇三磷酸酯的形成。出乎意料的是，所有具有GαzN末端一半的嵌合体均无法与PLCβ2功能结合，尽管事实上许多嵌合体都包含来自Gα14的核心与PLCβ相互作用的残基。进一步的分析表明，非PLCβ2相互作用的嵌合体能够与其他效应分子（例如腺苷酸环化酶和四肽重复序列1）相互作用，表明它们可以采用与GTP结合的活性构象。结论总体而言，我们的研究表明，先前确定的与PLCβ相互作用的残基不足以确保Gα14与PLCβ的有效相互作用，