Structures of the Rhodopsin-Transducin Complex: Insights into G-Protein Activation
Structures of the Rhodopsin-Transducin Complex: Insights into G-Protein Activation
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DOI：
10.1016/j.molcel.2019.06.007
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发表时间：
2019-08-22
期刊：
影响因子：
16
通讯作者：
Skiniotis, Georgios
中科院分区：
文献类型：
--
作者：
Gao, Yang;Hu, Hongli;Skiniotis, Georgios
视紫红质（Rho）是脊椎动物视觉中的一种典型的G蛋白偶联受体（GPCR），通过催化G蛋白转导素（G（T））α亚基（G α（T））上的GDP-GTP交换来激活G蛋白转导素（G（T））。为了阐明G（T）偶联和活化的决定因素，我们在存在和不存在G蛋白稳定纳米抗体的情况下获得了全功能光活化Rho-G（T）复合物的冷冻电镜结构。这些结构说明了G（T）如何通过以不同于其他GPCR-G-蛋白复合物的构象接合活化的Rho来克服其低基础活性。此外，无纳米抗体的结构揭示了G蛋白组分的天然构象，并捕获了三种不同的构象异构体，显示GMT螺旋结构域（α HD）接触G β γ亚基。这些发现揭示了视紫红质激活G蛋白的分子基础，并揭示了G β γ在受体催化的核苷酸交换过程中所起的作用。
Rhodopsin (Rho), a prototypical G-protein-coupled receptor (GPCR) in vertebrate vision, activates the G-protein transducin (G(T)) by catalyzing GDP-GTP exchange on its alpha subunit (G alpha(T)). To elucidate the determinants of G(T) coupling and activation, we obtained cryo-EM structures of a fully functional, light-activated Rho-G(T) complex in the presence and absence of a G-protein-stabilizing nanobody. The structures illustrate how G(T) overcomes its low basal activity by engaging activated Rho in a conformation distinct from other GPCR-G-protein complexes. Moreover, the nanobody-free structures reveal native conformations of G-protein components and capture three distinct conformers showing the GMT helical domain (alpha HD) contacting the G beta gamma subunits. These findings uncover the molecular underpinnings of G-protein activation by visual rhodopsin and shed new light on the role played by G beta gamma during receptor-catalyzed nucleotide exchange.