Tertiary structure modelling of active G protein coupled receptor states

G蛋白偶联受体（gpcr）通过激活胞内G蛋白(G)或阻滞蛋白（Arr）将胞外信号转导到细胞内。目前25种不同的非活性受体状态的高分辨率结构揭示了跨膜螺旋（TM）的共同拓扑结构，即使是远亲gpcr。在激动剂结合受体的x射线结构中，甚至保留了非活性状态的拓扑结构。只有在gpcr与G或Arr或模拟蛋白或片段共晶中，受体才表现出活性态构象（R*），其标志是TM5和7的重排和TM6的向外倾斜。相比之下，最近的核磁共振波谱和分子动力学模拟表明，在没有G或Arr的情况下，R*具有多种构象态和基态。G或Arr特异性结合的选择状态已经存在于典型的光感受器视紫红质或β -肾上腺素感受器的构象空间中。为了阐明gpcr大超家族中其他成员R*态的构象空间，并模拟它们与G或Arr的相互作用，计算生物物理学和生物信息学方法将在这里结合起来。我们将开发和应用新的计算工具，例如，研究水介导的氢键网络和受体空隙在激活和偏置信号传导中的作用。该项目的主要目的是阐明GPCR大超家族与G或Arr之间差异相互作用的关键决定因素，最终调节受体激活不同下游信号通路的功效。

G protein coupled receptors (GPCRs) transduce extracellular signals into the cell through activation of intracellular G proteins (G) or arrestins (Arr). High resolution structures of currently 25 different inactive receptor states reveal a common topology of transmembrane helices (TM) even of distantly related GPCRs. The topology of the inactive state is even preserved in X-ray structures of agonist bound receptors. Only in co-crystals of GPCRs with G or Arr or mimicking proteins or fragments, the receptor exhibits the active state conformation (R*), which hallmarks are rearrangements of TM5 and 7 and outward tilting of TM6. By contrast, recent nuclear magnetic resonance spectroscopy and molecular dynamics simulations reveal that the R* samples several conformational states and substates in the absence of G or Arr. The states selected for specific binding of G or Arr are already present within the conformational space of the prototypical photoreceptor rhodopsin or the beta2-adrenoceptor. To elucidate the conformational space of R* states of other members of the large super-family of GPCRs and to model their interactions with G or Arr, computational biophysics and bioinformatics approaches will be combined here. We will develop and apply novel computational tools e.g. to investigate the role of water mediated hydrogen bonding networks and receptor voids for activation and biased signalling. The principle objective of this project is to elucidate the key determinants for differential interactions of the large GPCR super-family with G or Arr, eventually modulating the receptors' efficacy to activate different downstream signalling pathways.