Understanding the molecular basis of partial agonism and G protein selectivity in GPCRs

BBSRC战略主题：了解lifeG蛋白偶联受体（GPCR）的规则是膜嵌入的信号蛋白，当被激动剂激活时，它们会改变构象，使异源三聚体G蛋白或抑制蛋白等转换器能够结合。结构和生物物理数据提供了广泛的洞察力如何激动剂影响GPCR的功能。然而，受体的构象变化如何影响耦合和激活的细胞内转导仍然知之甚少。主要的问题仍然存在，例如为什么某些激动剂产生不到完全的反应（称为部分激动），以及为什么给定的受体选择性地结合G蛋白家族的一种特定亚型而不是另一种（信号偏差）。目前，我们依赖于来自固定蛋白质静态结构的信息，但为了回答这些问题，我们需要对GPCR-G蛋白复合物的更多了解，以揭示其真正的动态性质。该项目将使用核磁共振研究这些方面，以提供急需的动态解释GPCR和G蛋白如何相互作用。一系列激动剂和不同的G蛋白的复合物将进行研究，以建立构象变异性如何出现。然后，分子观察结果将与各种生物物理特性相关，例如与信号功能相关的结合亲和力、交换动力学和核苷酸交换率等。使用溶液NMR数据，将建立b1 AR-G蛋白质复合物的3D模型结构。总之，这项工作将提供一个动态的角度GPCR-G蛋白复合物，并揭示部分激动和G蛋白选择性的关键分子特征。

BBSRC strategic theme: Understanding the rules of lifeG protein-coupled receptors (GPCRs) are membrane-embedded signaling proteins that, when activated by agonists change their conformation, enabling transducers such as heterotrimeric G proteins or arrestins to bind. Structural and biophysical data have provided extensive insight into how agonists affect the function of GPCRs. However, how conformational changes in the receptor affect coupling and activation of intracellular transducers remains poorly understood. Major questions remain such as why certain agonists produce a less than full response (known as partial agonism), and why a given receptor binds selectively to one particular subtype of the G protein family over another (signal bias). Currently, we are reliant on information from static structures of immobilised proteins but to answer these questions we need additional insight on GPCR-G protein complexes that reveals their true dynamic nature.The project will investigate these aspects using NMR, to provide a much-needed dynamic explanation of how GPCRs and G proteins interact. A range of agonists and complexes with different G proteins will be investigated to establish how conformational variability arises. The molecular observations will then be related to various biophysical properties, such as binding affinity, kinetics of exchange and nucleotide exchange rates etc. that link to signaling function. Using the solution NMR data 3D model structures of b1AR-G protein complexes will be built. Overall, this work will provide a dynamic perspective of GPCR-G protein complexes and reveal key molecular features of partial agonism and G protein selectivity.