Molecular view on binding and unbinding processes between the human β2-adrenergic receptor and its cognate G protein at different stages of the activation cycle

细胞对细胞外刺激的反应能力是由附着在细胞膜上的复杂蛋白质机制实现的。该机制的核心是跨膜蛋白G蛋白偶联受体及其相关的G蛋白，本项目旨在阐明G蛋白与一种重要的G蛋白偶联受体β2-肾上腺素能受体在不同的激活周期和膜环境中结合和解离过程的途径和潜在的自由能景观。这些结果有望提供新的重要细节的信号从细胞外部到细胞内部的传输机制和其调制膜composition.Using原子和粗粒度的分子动力学模拟，我们将解决的组装，结构和稳定性的信号复合物之前和之后的受体激活和稳定的中间复合物。模拟将提供分子决定因素的G蛋白对受体的影响和原子论的观点（联合国）结合途径。此外，通过系统地改变膜组成的特异性和非特异性的影响，不同的脂质和胆固醇的受体和G蛋白之间的相互作用将被阐明。由丹尼尔Müller教授的主持小组进行的互补多功能原子力显微镜成像将用于获得G蛋白与受体沿着解离/缔合途径的结合力曲线。此外，委员会认为，动态单分子力谱将被应用于研究G蛋白在受体激活周期的不同阶段的（去）稳定作用。这项合作努力-结合分子动力学模拟和原子力显微镜-旨在提供关于G蛋白偶联受体组装和拆卸的原子分辨率的第一个信息。G蛋白信号复合物及其脂质调节作用。

The ability of a cell to react to extracellular stimuli is enabled by a complex protein machinery attached to the cell membrane. The core of this machinery consists of transmembrane proteins termed G protein-coupled receptors and their associated G proteins found in the cell interior.This project aims at deciphering the pathways and the underlying free-energy landscapes of the binding and unbinding processes between a G protein and a prominent G-protein coupled receptor, β2-adrenergic receptor, at different stages of the activation cycle and in various membrane environments. The results are expected to provide new important details on the mechanism of signal transmission from the cell exterior to the cell interior and its modulation by membrane composition.Using both atomistic and coarse-grained molecular dynamics simulations we will address the assembly, the structure, and the stability of the signaling complex before and after receptor activation and the stability of the intermediate complex. Simulations will deliver molecular determinants of the G protein-exerted effects on the receptor and an atomistic view on the (un)binding pathways. Moreover, by systematically varying the membrane composition both specific and unspecific effects of different lipids and cholesterol on the interactions between the receptor and the G protein will be elucidated. Complementary multifunctional atomic force microscopy imaging, performed by the host group of Prof. Daniel Müller, will be used to obtain binding force profiles of the G protein to the receptor along the dissociation/association pathways. Moreover, dynamic single-molecule force spectroscopy will be applied to study (de)stabilization effects of the G protein on the receptor at different stages of the activation cycle.This collaborative effort - combining molecular dynamics simulations and atomic force miscroscopy - aims to provide first information at atomistic resolution on the assembly and disassembly of the G protein-coupled receptor/G protein signaling complex and lipid modulation effects thereon.