Selective Gene Regulation by Manganese and Iron in Bacillus subtilis

枯草芽孢杆菌中锰和铁的选择性基因调控

• 批准号: 9630411
• 负责人: John Helmann
• 金额: --
• 依托单位: Cornell Univ - State: AWDS MADE PRIOR MAY 2010
• 依托单位国家: 美国
• 项目类别: Continuing grant
• 财政年份: 1997
• 资助国家: 美国
• 起止时间: 1997-01-15 至 1999-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9630411&HistoricalAwards=false
• 关键词: Selective; Gene; Regulation; Manganese; Iron

Helmann 9630411 Bacillus subtilis provides a genetically well-characterized model organism ideal for analyzing the complexities of gene regulation. Previous work has defined two sets of genes regulated by metal ion availability: (i) genes involved in iron uptake which are repressed by a Fur homolog and (ii) genes involved in protection against oxidative stress which are repressed by a protein designated PerR in the presence of manganese, iron or certain other divalent metal ions. In this project, the B.subtilis Fur protein will be identified and characterized. The furA and furB genes, identified as part of the B. subtilis genome project, encode proteins homologous to the Fur family of metal-activated repressor proteins and are likely candidates for the fur and perR genes. A genetic approach will be pursued to identify regulatory factors influencing the Fur and PerR regulons. Biochemical characterization of Fur will reveal the molecular basis of its DNA and metal-binding selectivity. The iron specificity of the Fur regulon presumably results from an ability of this metalloregulatory protein to discriminate against chemically related transition metals. This contrasts with the relatively broad metal selectivity of DtxR and E.coli Fur. The broad metal selectivity of the peroxide regulon is imparted by PerR, which is hypothesized to be a relatively non-specific metal-binding protein which acts as a molecular sensor of the simultaneous presence of redox active metal ions and hydrogen peroxide. Metal ions are essential cofactors for many of the chemical transformations required for life, including the processes of respiration, DNA replication, and transcription. In particular, iron is of vanishingly low solubility in the presence of oxygen and near neutral pH and frequently limits the growth of bacteria both in the environment and, in the case of pathogenic organisms, in the host. Bacteria have evolved a highly sophisticated strategy to obtain iron from the environment by the synthesis, excretion, and readsorption of iron specific organic chelators known as siderophores. This process is highly regulated, since just as low iron can limit growth, an overabundance of intracellular iron can lead to deleterious chemical reactions that damage membranes and DNA. These harmful side reactions frequently involve reactive oxygen species. There is an emerging realization that metal ion homeostasis is frequently coordinated with systems designed to handle reactive oxygen species. This research explores the genetic mechanisms which control iron homeostasis in Bacillus subtilis, a gram positive soil micoorganism, and the relationship between iron homeostasis and cellular defenses against oxidative damage.

Helmann 9630411枯草芽孢杆菌为分析基因调控的复杂性提供了理想的遗传上充分表征的模式生物。以前的工作已经定义了两组受金属离子可用性调节的基因：（i）参与铁摄取的基因，其被Fur同系物抑制;和（ii）参与保护免受氧化应激的基因，其在锰、铁或某些其他二价金属离子存在下被称为PerR的蛋白质抑制。在本项目中，将鉴定和表征B.subtilis Fur蛋白。furA和furB基因，鉴定为B的一部分。枯草杆菌基因组计划，编码与金属激活阻遏蛋白的Fur家族同源的蛋白质，并且可能是fur和perR基因的候选者。遗传学的方法将被追求，以确定影响Fur和PerR调节子的调控因素。毛皮的生化特性将揭示其DNA和金属结合选择性的分子基础。铁的特异性的毛皮调节子可能是由于这种金属调节蛋白的能力，以歧视化学相关的过渡金属。这与DtxR和大肠杆菌Fur的相对广泛的金属选择性形成对比。过氧化物调节子的宽金属选择性由PerR赋予，PerR被假设为是相对非特异性的金属结合蛋白，其充当氧化还原活性金属离子和过氧化氢同时存在的分子传感器。金属离子是生命所需的许多化学转化的重要辅助因子，包括呼吸，DNA复制和转录过程。特别地，铁在氧气存在和接近中性pH的情况下溶解度非常低，并且经常限制环境中细菌的生长，并且在病原生物体的情况下，限制宿主中细菌的生长。细菌已经进化出一种高度复杂的策略，通过合成、排泄和再吸附铁特异性有机螯合剂（称为铁载体）从环境中获得铁。这个过程是高度调节的，因为就像低铁会限制生长一样，细胞内过量的铁会导致有害的化学反应，破坏细胞膜和DNA。这些有害的副反应通常涉及活性氧物质。有一个新兴的认识，即金属离子稳态经常与设计来处理活性氧的系统相协调。本研究探讨了控制枯草芽孢杆菌（一种革兰氏阳性土壤微生物）铁稳态的遗传机制，以及铁稳态与细胞防御氧化损伤之间的关系。