Institute for Cell and Molecular Biosciences, Newcastle University, Newcastle upon Tyne NE2 4HH, UK.
Biochem Soc Trans. 2010 Aug;38(4):928-33. doi: 10.1042/BST0380928.
The stressosome co-ordinates the response of Bacillus subtilis to the imposition of a variety of physical and environmental insults. These stresses include fluctuations in salt concentration, the presence of ethanol, changes in pH and even the level of UV light. Despite the obvious and significant differences between these quite different physicochemical stimuli, the result is the same: the stressosome is phosphorylated by a key kinase to initiate the sigma(B) cascade. The phosphorylation of the stressosome initiates a signal transduction system that up-regulates the expression of stress-responsive genes so that the Bacillus can survive the imposition of stress. Hence the stressosome acts as a hub, receiving manifold different stimuli to effect a single outcome. Using single-particle analysis of cryo-electron micrographs, we have been able to reconstruct a series of molecular envelopes of the stressosome. These maps have been interpreted at near-atomic resolution with crystal structures of the individual components of the stressosome to provide the first visualization of this unique signalling hub. The macromolecular structure adopted by the stressosome provides the signalling cascade with the potential for co-operative behaviour, which we have also measured in live bacteria. These experiments are consistent with the tuning of the response of B. subtilis to stress relative to the magnitude of the insult.
应激体协调枯草芽孢杆菌对各种物理和环境胁迫的反应。这些压力包括盐浓度的波动、乙醇的存在、pH 值的变化，甚至紫外线水平的变化。尽管这些截然不同的物理化学刺激之间存在明显而显著的差异，但结果是相同的：应激体被关键激酶磷酸化，从而启动σ(B)级联反应。应激体的磷酸化启动了一个信号转导系统，上调应激反应基因的表达，使枯草芽孢杆菌能够在应激作用下存活。因此，应激体充当了一个枢纽，接收多种不同的刺激，以达到单一的结果。我们使用冷冻电子显微镜的单颗粒分析，已经能够重建应激体的一系列分子包络。这些图谱已经通过应激体各个组件的晶体结构进行了近乎原子分辨率的解释，从而首次可视化了这个独特的信号枢纽。应激体采用的大分子结构为信号级联提供了协同作用的潜力，我们在活细菌中也测量到了这种协同作用。这些实验与枯草芽孢杆菌对压力的反应相对于压力大小的调整是一致的。
