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微量金属，但这些相同的金属，如果过量存在，通常会通过催化有毒自由基的形成而导致毒性。特别是铁和铜，可以通过促进高活性羟基自由基的产生来加剧氧化应激。相比之下，锰和锌实际上可以保护细胞免受氧化应激。枯草芽孢杆菌含有两个由过氧化物胁迫选择性诱导的调节子（PerR和OhrR）和至少两个由一氧化氮诱导的调节子（PerR和Fur）。该项目的重点是两个调节器，反应活性氧：PerR和OhrR。过氧化物调节子（PerR）阻遏物在结构上与Fur相关，但PerR在生理上作为过氧化应激的传感器发挥作用，而不是金属离子饥饿。有人提出，PerR，与金属结合的辅因子，与过氧化氢反应，产生一个无活性的阻遏物。将定义导致去阻遏的PerR变化的性质。OhrR蛋白含有高度反应性的半胱氨酸残基，其与有机过氧化物反应以产生半胱氨酸-次磺酸衍生物。这种蛋白质修饰使阻遏物失活，导致有机氢过氧化物抗性基因的表达。将研究半胱氨酸氧化对OhrR功能的影响。拟议的研究将提供深入了解蛋白质如何作为活性氧/氮物质的传感器。在不同的细菌中存在相关的监管机构认为，这些蛋白质的详细表征所建立的范式将具有深远的影响。

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.