The activation mechanism of the Bacillus subtilis stressosome signalling hub

所有生物的生存都依赖于它们适应环境变化的能力和枯草芽孢杆菌的应激反应，以及它的一些革兰氏阳性亲缘菌，为这些生物提供了一种保护机制，以应对各种物理和化学应激。本研究计划关注枯草芽孢杆菌对环境刺激的反应机制。在应激反应途径的顶端是一个类似于小病毒的结构，充当信号中枢，并被命名为应激体。这种应激小体由许多感知应激诱导刺激的蛋白质组成，这些蛋白质与一种名为RsbR的蛋白质和另一种名为RsbS的小蛋白质有关，它们共同作用于隔离一种名为RsbT的蛋白激酶，这种蛋白激酶需要启动一连串的相互作用，最终导致超过200个基因的激活，这些基因的产物为细胞提供抗应激能力。我们最近确定的应激体的结构显示出一种不寻常的蛋白质成分排列，为应激反应的作用机制提供了诱人的线索。我们的目标是使用蓝光响应信号蛋白来产生应激小体，我们可以在结构研究中使用它来确定导致蛋白激酶释放的复合物中的任何总体结构变化，从而确定启动应激反应的机制。此外，我们将通过产生仅由rsbr样蛋白组成的应激小体来研究RsbS蛋白在应激反应中的作用，RsbS蛋白的缺失会导致细菌发育成小而病态的细胞。与RsbR相关的蛋白也可能作为信号模块发挥作用。对这些蛋白质如何工作的充分理解依赖于x射线晶体学对其结构的确定，x射线晶体学提供了蛋白质的分子模型，可用于评估通过其特定形状识别的潜在激活信号。最后，我们将研究一些已知介导应激信号长度的其他蛋白质的作用，因为及时关闭应激反应的要求几乎与首先对应激作出反应的能力一样重要。

The survival of all organisms is dependent on their ability to adapt to changes in their environment and the stress response of Bacillus subtilis, and a number of its close Gram-positive relatives, provides these organisms with a protective mechanism against a wide range of physical and chemical stresses. This research proposal concerns the mechanism by which B. subtilis is able to respond to environmental stimuli. At the top of the stress-response pathway is a structure resembling a small virus that acts as a signalling hub, and has been named the stressosome. This stressosome is composed of a number of proteins that sense stress-inducing stimuli that are related to a protein called RsbR and another small protein, RsbS, that together act to sequester a protein kinase, RsbT, required to kick-start a cascade of interactions that ultimately leads to the activation of over two hundred genes whose products provide the cell with resistance to stress. The structure of the stressosome that we have recently determined, displays an unusual arrangement of protein components providing tantalising clues as to the mechanism of action in response to stress. We aim to use a blue-light responsive signalling protein to generate a stressosome that we can use in structural studies to determine any gross-structural changes in the complex that lead to the release of the protein kinase and thus the mechanism by which the stress response is initiated. Furthermore, we will investigate the role of the RsbS protein, the absence of which causes bacteria to develop as small and sickly cells, in stress-response by creating stressosomes that consist only of an RsbR-like protein. It is also apparent that the proteins related to RsbR may function as signalling modules. A full understanding of how these proteins work is dependent on the determination of their structures by X-ray crystallography, which provides a molecular model of the protein that can be used to assess potential activating signals that are recognised by their specific shapes. Finally, we will investigate the role of a number of other proteins that are known to mediate the length of the stress signal, as the requirement to turn off the stress response in a timely fashion is almost as important as the ability to respond to stress in the first place.