Physical Chemistry I, Ruhr-University Bochum, 44780, Bochum, Germany.
Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, NC27710, USA.
J Mol Biol. 2020 Mar 27;432(7):2164-2185. doi: 10.1016/j.jmb.2020.02.009. Epub 2020 Feb 19.
The human guanylate-binding protein 1 (hGBP1) belongs to the dynamin superfamily proteins and represents a key player in the innate immune response. Farnesylation at the C-terminus is required for hGBP1's activity against microbial pathogens, as well as for its antiproliferative and antitumor activity. The farnesylated hGBP1 (hGBP1) retains many characteristics of the extensively studied nonfarnesylated protein and gains additional abilities like binding to lipid membranes and formation of hGBP1 polymers. These polymers are believed to serve as a protein depot, making the enzyme immediately available to fight the invasion of intracellular pathogens. Here we study the molecular mechanism of hGBP1 polymer formation as it is a crucial state of this enzyme, allowing for a rapid response demanded by the biological function. We employ Förster resonance energy transfer in order to trace intra and intermolecular distance changes of protein domains. Light scattering techniques yield deep insights into the changes in size and shape. The GTP hydrolysis driven cycling between a closed, farnesyl moiety hidden state and an opened, farnesyl moiety exposed state represents the first phase, preparing the molecule for polymerization. Within the second phase of polymer growth, opened hGBP1 molecules can be incorporated in the growing polymer where the opened structure is stabilized, similar to a surfactant molecule in a micelle, pointing the farnesyl moieties into the hydrophobic center and positioning the head groups at the periphery of the polymer. We contribute the molecular mechanism of polymer formation, paving the ground for a detailed understanding of hGBP1 function.
人鸟苷酸结合蛋白 1（hGBP1）属于动力蛋白超家族蛋白，是先天免疫反应的关键因子。C 末端的法尼基化对于 hGBP1 对抗微生物病原体的活性以及其抗增殖和抗肿瘤活性都是必需的。法尼基化的 hGBP1（hGBP1）保留了广泛研究的非法尼基化蛋白的许多特性，并获得了额外的能力，如与脂质膜结合和形成 hGBP1 聚合物。这些聚合物被认为是一种蛋白质储存库，使酶能够立即用于对抗细胞内病原体的入侵。在这里，我们研究 hGBP1 聚合物形成的分子机制，因为它是该酶的关键状态，允许酶对生物功能所需的快速反应。我们采用Förster 共振能量转移来追踪蛋白质结构域的分子内和分子间距离变化。光散射技术深入了解尺寸和形状的变化。GTP 水解驱动的封闭、隐藏法尼基部分状态和打开、暴露法尼基部分状态之间的循环代表第一阶段，为聚合作用做准备。在聚合物生长的第二阶段，打开的 hGBP1 分子可以被纳入正在生长的聚合物中，其中打开的结构得到稳定，类似于胶束中的表面活性剂分子，将法尼基部分指向疏水性中心，并将头部基团定位在聚合物的外围。我们提出了聚合物形成的分子机制，为深入了解 hGBP1 功能奠定了基础。
