Molecular mechanism of Gαi activation by non-GPCR proteins with a Gα-Binding and Activating motif.
Molecular mechanism of Gαi activation by non-GPCR proteins with a Gα-Binding and Activating motif.
复制标题
DOI：
10.1038/ncomms15163
复制
发表时间：
2017-05-18
影响因子：
16.6
通讯作者：
Garcia-Marcos M
中科院分区：
文献类型：
--
作者：
de Opakua AI;Parag-Sharma K;DiGiacomo V;Merino N;Leyme A;Marivin A;Villate M;Nguyen LT;de la Cruz-Morcillo MA;Blanco-Canosa JB;Ramachandran S;Baillie GS;Cerione RA;Blanco FJ;Garcia-Marcos M
异三聚体 G 蛋白是通过 Gα 上的核苷酸交换激活的典型信号传导开关。尽管激活主要由 G 蛋白偶联受体 (GPCR) 进行，但非受体鸟嘌呤核苷酸交换因子 (GEF) 已成为关键的信号分子和治疗靶点。在这里，我们描述了包含 Gα 结合和激活 (GBA) 基序的非受体 GEF 家族激活 G 蛋白的分子机制。我们结合 NMR 光谱、计算模型和生物化学，以残基水平分辨率绘制由 GBA 蛋白结合引起的 Gα 变化。我们发现 GBA 基序与 Gα 的 SwitchII/α3 裂口结合，并诱导 G-1/P 环和 G-2 盒（涉及磷酸盐结合）的变化，但不诱导 G-4/G-5 盒（鸟嘌呤结合）的变化。我们的研究结果表明，GBA 蛋白和 GPCR 之间的 G 蛋白结合和激活机制根本不同，并且 GEF 介导的核苷酸磷酸结合扰动足以激活 Gα。非受体鸟嘌呤核苷酸交换因子 (GEF) 正在成为异三聚体 G 蛋白的重要调节因子。在这里，作者提出了关于一类包含 Ga 结合和激活基序的非受体 GEF 如何相互作用和调节 G 蛋白的结构和机制见解。
Heterotrimeric G proteins are quintessential signalling switches activated by nucleotide exchange on Gα. Although activation is predominantly carried out by G-protein-coupled receptors (GPCRs), non-receptor guanine-nucleotide exchange factors (GEFs) have emerged as critical signalling molecules and therapeutic targets. Here we characterize the molecular mechanism of G-protein activation by a family of non-receptor GEFs containing a Gα-binding and -activating (GBA) motif. We combine NMR spectroscopy, computational modelling and biochemistry to map changes in Gα caused by binding of GBA proteins with residue-level resolution. We find that the GBA motif binds to the SwitchII/α3 cleft of Gα and induces changes in the G-1/P-loop and G-2 boxes (involved in phosphate binding), but not in the G-4/G-5 boxes (guanine binding). Our findings reveal that G-protein-binding and activation mechanisms are fundamentally different between GBA proteins and GPCRs, and that GEF-mediated perturbation of nucleotide phosphate binding is sufficient for Gα activation. Nonreceptor guanine-nucleotide exchange factors (GEFs) are emerging as important regulators of heterotrimeric G proteins. Here, the authors present structural and mechanistic insights into how a class of nonreceptor GEFs containing the Ga-Binding and Activating motif interact and modulate G proteins.