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

BBSRC战略主题：了解生命的规则G蛋白偶联受体(GPCRs)是一种膜嵌入的信号蛋白，当被激动剂激活时，改变其构象，使转导蛋白如异源三聚体G蛋白或拦阻蛋白结合。结构和生物物理数据为激动剂如何影响GPCRs的功能提供了广泛的见解。然而，受体的构象变化如何影响细胞内转导分子的偶联和激活仍然知之甚少。主要的问题仍然存在，例如为什么某些激动剂产生的反应不完全(称为部分激动症)，以及为什么给定的受体选择性地与G蛋白家族的一个特定亚型结合而不是另一个亚型(信号偏差)。目前，我们依赖于来自固定化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蛋白质复合体的更多了解，以揭示其真实的动态性质。该项目将使用核磁共振研究这些方面，以提供亟需的GPCRs和G蛋白质如何相互作用的动态解释。将研究一系列激动剂和与不同G蛋白的复合体，以确定构象可变性是如何产生的。分子观察将与各种生物物理性质有关，如与信号功能有关的结合亲和力、交换动力学和核苷酸交换率等。利用溶液核磁共振数据，建立b1AR-G蛋白复合体的三维模型结构。总体而言，这项工作将提供GPCR-G蛋白复合体的动态视角，并揭示部分激动性和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.