Activation of the Galpha subunit of heterotrimeric GTP-binding proteins by transmembrane receptors requires the propagation of structural signals from the receptor-binding site to the nucleotide-binding site at the opposite side of the protein. In a previous model, it was suggested that the Gbeta-Ggamma dimer is tilted away from Galpha by a lever-arm motion of the Galpha N-terminal helix. Here, we propose that the motion occurs in the opposite direction, close-packing the Galpha-Gbeta interface and creating a novel interface between the helical domain of Galpha and the N terminus of Ggamma, which determines the specificity of activation.

中文翻译：

---

受体通过Galpha-Gbeta和Galpha-Ggamma相互作用激活G蛋白Galpha亚基。

跨膜受体对异源三聚体GTP结合蛋白的Galpha亚基的激活需要将结构信号从受体结合位点传播到蛋白相对侧的核苷酸结合位点。在以前的模型中，建议通过Galpha N末端螺旋的杠杆臂运动使Gbeta-Gamma二聚体倾斜远离Galpha。在这里，我们建议运动发生在相反的方向，紧密堆积Galpha-Gbeta界面，并在Galpha的螺旋域和Ggamma的N末端之间创建一个新颖的界面，从而确定激活的特异性。