Department of Molecular Physiology and Biophysics, University of Iowa Carver College of Medicine, Iowa City, IA, 52242, USA.
Department of Biochemistry, University of Iowa Carver College of Medicine, Iowa City, IA, 52242, USA.
Nat Commun. 2019 Jul 12;10(1):3084. doi: 10.1038/s41467-019-11088-x.
Resistance to inhibitors of cholinesterase 8A (Ric8A) is an essential regulator of G protein α-subunits (Gα), acting as a guanine nucleotide exchange factor and a chaperone. We report two crystal structures of Ric8A, one in the apo form and the other in complex with a tagged C-terminal fragment of Gα. These structures reveal two principal domains of Ric8A: an armadillo-fold core and a flexible C-terminal tail. Additionally, they show that the Gα C-terminus binds to a highly-conserved patch on the concave surface of the Ric8A armadillo-domain, with selectivity determinants residing in the Gα sequence. Biochemical analysis shows that the Ric8A C-terminal tail is critical for its stability and function. A model of the Ric8A/Gα complex derived from crosslinking mass spectrometry and molecular dynamics simulations suggests that the Ric8A C-terminal tail helps organize the GTP-binding site of Gα. This study lays the groundwork for understanding Ric8A function at the molecular level.
对胆碱酯酶抑制剂 8A（Ric8A）的抗性是 G 蛋白 α-亚基（Gα）的重要调节剂，作为鸟嘌呤核苷酸交换因子和伴侣发挥作用。我们报告了 Ric8A 的两个晶体结构，一个是apo 形式，另一个是与 Gα 的标记 C 末端片段的复合物。这些结构揭示了 Ric8A 的两个主要结构域：一个鳞甲样核心和一个灵活的 C 末端尾巴。此外，它们表明 Gα C 末端结合到 Ric8A 鳞甲结构域的凹面高度保守的斑块上，选择性决定因素存在于 Gα 序列中。生化分析表明，Ric8A C 末端尾巴对于其稳定性和功能至关重要。来自交联质谱和分子动力学模拟的 Ric8A/Gα 复合物模型表明，Ric8A C 末端尾巴有助于组织 Gα 的 GTP 结合位点。这项研究为在分子水平上理解 Ric8A 的功能奠定了基础。
