Selective Gene Regulation by Manganese and Iron in Bacillus subtilis

所有生物都必须从其环境中获得一组特定的微量金属。因此，细胞必须能够感知单个金属离子的细胞内水平，以便适当地协调金属离子转运、储存和细胞内运输。细胞金属离子水平由抑制或激活金属离子稳态基因表达的金属调节蛋白监测。在枯草芽孢杆菌中，四种不同的金属调节剂控制锌、铁和锰的转运，并调节氧化应激反应。该项目涉及两种调节因子Fur和PerR蛋白的生物学作用和机制。铁摄取抑制蛋白（Fur）作为铁依赖性抑制蛋白协调铁摄取功能的表达。然而，最近的生物化学研究表明，毛皮紧密结合到其目标运营商网站独立的铁。这表明，在细胞中，Fur的活性受到其他因素的调节，可能是金属离子，拮抗这种内在的DNA结合活性。过氧化物调节子（PerR）阻遏物在结构上与Fur相关。然而，PerR在生理上作为氧化应激的传感器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。导致去阻遏的PerR变化的性质目前尚不清楚。在这个项目中，铁传感的分子基础，由毛皮，和过氧化物传感，由PerR，将使用分子遗传学和生物化学方法相结合的研究。这些研究将为蛋白质如何选择性地与细胞中的不同金属离子结合以及它们如何利用金属离子作为氧化应激的传感器提供见解。在不同的细菌中存在相关的调节因子，这表明通过对B.枯草杆菌监管机构将有深远的影响。

All organisms must obtain a specific set of trace metals from their environment. Accordingly, cells must be able to sense the intracellular level of individual metal ions in order to properly coordinate metal ion transport, storage, and intracellular trafficking. Cellular metal ion levels are monitored by metalloregulatory proteins that repress or activate the expression of metal ion homeostasis genes. In Bacillus subtilis, four distinct metalloregulators control the transport of zinc, iron, and manganese and regulate an oxidative stress response. This project addresses the biological roles and mechanisms of two regulators, the Fur and PerR proteins. The ferric uptake repressor (Fur) protein coordinates the expression of iron uptake functions by acting as an iron-dependent repressor. However, recent biochemical studies indicate that Fur binds tightly to its target operator sites independently of iron. This suggests that in the cell the activity of Fur is regulated by other factors, perhaps a metal ion, that antagonize this intrinsic DNA-binding activity. The peroxide regulon (PerR) repressor is structurally related to Fur. However, PerR functions physiologically as a sensor of oxidative 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 are currently unknown. In this project, the molecular basis for Fe-sensing, by Fur, and peroxide-sensing, by PerR, will be investigated using a combination of molecular genetic and biochemical approaches. These studies will provide insights into how proteins bind selectively to different metal ions in the cell and how they can use metal ions to serve as sensors of oxidative stress. The presence of related regulators in diverse bacteria argues that the paradigms established by a detailed characterization of the B. subtilis regulators will have far-reaching implications.