Gene Regulation by Oxidative Stress in Bacillus Subtilis

所有生物体都必须从其环境中获得一组特定的痕量金属，但这些金属如果过量存在，往往会通过催化有毒自由基的形成而导致毒性。尤其是铁和铜，会导致高活性羟基自由基的产生，从而加剧氧化应激。相比之下，锰和锌实际上可以保护细胞免受氧化应激的伤害。枯草芽孢杆菌含有两个受过氧化氢胁迫选择性诱导的调节子(PerR和OhrR)和至少两个受一氧化氮诱导的调节子(PerR和Fur)。本项目重点研究了两种对活性氧物种作出反应的调节剂：PERR和OHRR。过氧化调节蛋白(PERR)阻遏物在结构上与毛皮有关，但PERR在生理上是过氧化应激的感受器，而不是金属离子饥饿。有人认为，PerR与一个金属结合的辅因子一起，与过氧化氢反应生成一个非活性的抑制子。导致去抑制的Perr变化(S)的性质将被定义。OhrR蛋白含有一个高活性的半胱氨酸残基，它与有机过氧化物反应生成半胱氨酸-磺酸衍生物。这种蛋白质修饰使阻遏物失活，导致有机抗过氧化氢基因的表达。半胱氨酸氧化对OhrR功能的影响将被研究。拟议的研究将为蛋白质如何作为活性氧/氮物种的传感器提供见解。相关调控因子在不同细菌中的存在表明，通过对这些蛋白质的详细表征而建立的范例将具有深远的影响。

All organisms must obtain a specific set of trace metals from their environment yet these same metals, if present in excess, can lead to toxicity often by catalyzing the formation of toxic free radicals. Iron and copper, in particular, can aggravate oxidative stress by contributing to the generation of highly reactive hydroxyl radicals. In contrast, manganese and zinc can actually protect cells against oxidative stress. Bacillus subtilis contains two regulons that are selectively induced by peroxide stress (PerR and OhrR) and at least two regulons induced by nitric oxide (PerR and Fur). This project focuses on two regulators that respond to reactive oxygen species: PerR and OhrR. The peroxide regulon (PerR) repressor is structurally related to Fur but PerR functions physiologically as a sensor of peroxidative stress, rather than metal ion starvation. It is proposed that PerR, together with a metal bound cofactor, reacts with hydrogen peroxide to generate an inactive repressor. The nature of the change(s) in PerR that lead to derepression will be defined. The OhrR protein contains a highly reactive cysteine residue that reacts with organic peroxides to generate a cysteine-sulfenic acid derivative. This protein modification inactivates the repressor leading to expression of an organic hydroperoxide resistance gene. The effects of cysteine oxidation on OhrR function will be investigated. The proposed studies will provide insights into how proteins function as sensors of reactive oxygen/nitrogen species. The presence of related regulators in diverse bacteria argues that the paradigms established by a detailed characterization of these proteins will have far-reaching implications.