Iron Storage by Ferritin and Microbial Growth

铁蛋白和微生物生长的铁储存

• 批准号: RGPIN-2015-04802
• 负责人: Murphy, Michael
• 金额: $ 3.79万
• 依托单位: University of British Columbia
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2018
• 资助国家: 加拿大
• 起止时间: 2018-01-01 至 2019-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=660469
• 关键词: Iron; Storage; Ferritin; Microbial; Growth

Iron is essential for almost all forms of life. It is a cofactor for cell sustaining reactions such as mediating single electron transfer reactions of the electron transport chain or the formation of DNA building blocks by ribonucleotide reductases. The unique reactivity of metals such as iron necessitates control of uptake and intracellular handling to avoid toxic side effects. Understanding the cellular mechanisms of iron homeostasis in microbes is the central direction of my research and the focus of this research program is the role of ferritins.******Ferritins are iron storage proteins constructed of 12 or 24 subunits that assemble into a hollow sphere. Ferrous iron is oxidized to ferric ions by oxygen or hydrogen peroxide at ferroxidase sites before storage inside the sphere as an iron oxide mineral. By removing ferrous iron and consuming dioxygen or hydrogen peroxide, ferritins have an antioxidant role. Less is known about the mechanism of iron release from ferritin or how iron storage is regulated. I hypothesize that the mineral core of ferritin regulates the concentration of readily exchangeable cellular iron and that iron release is dependent on the reduction potential of the cell. Ferritin is proposed to be used by bloom-forming pennate diatoms to store excess iron for use in subsequent cell divisions thereby out competing centric diatoms that do not possess ferritin. Our hypothesis is that this ferritin has distinct functional features to supply iron to the photosynthetic machinery of the diatom. Escherichia coli has 3 different types of ferritin with potential distinct roles in iron storage and detoxification and is a model system to investigate ferritin function. ***Specific aims are:***1. To identify putative amino acid residues directly involved in Fe storage and release by ferritins by site-directed mutagenesis. Crystal structures, kinetics of the ferroxidase reaction, iron mineralization, and iron release of recombinant wild-type and variants will assayed.***2. To show that a ferritin stores iron in cell, metal content analysis by ICP-MS will be done with native ferritin isolated from cells grown under varying iron availability and oxidative stress.***3. Iron release from ferritins will be examined by incubating iron loaded samples in the presence of physiological levels of ferrous iron chelating metabolites (eg. histidine) and reductants such as flavins and NAPH. A screen will be undertaken to search for proteins involved in iron release.***The results of this work will contribute to understanding of diatom blooms in the open ocean and the provide a foundation to understanding how pathogens cope with iron restriction imposed by host plants and animals. *** **

铁对几乎所有的生命形式都是必不可少的。它是细胞维持反应的辅因子，例如介导电子传递链的单电子转移反应或通过核糖核苷酸还原酶形成DNA结构单元。金属如铁的独特反应性需要控制摄取和细胞内处理以避免毒副作用。了解微生物中铁稳态的细胞机制是我研究的中心方向，这项研究计划的重点是铁蛋白的作用。铁蛋白是由12或24个亚基组成的铁储存蛋白，它们组装成一个中空的球体。亚铁在作为氧化铁矿物储存在球体内之前，在亚铁氧化酶位点被氧或过氧化氢氧化成三价铁离子。通过去除亚铁并消耗分子氧或过氧化氢，铁蛋白具有抗氧化作用。关于铁蛋白释放铁的机制或铁储存如何调节的知之甚少。我推测，铁蛋白的矿物核心调节易交换的细胞铁的浓度和铁的释放是依赖于细胞的还原电位。铁蛋白被提出用于形成水华的羽纹硅藻储存多余的铁用于随后的细胞分裂，从而淘汰不具有铁蛋白的竞争中心硅藻。我们的假设是，这种铁蛋白具有独特的功能特征，为硅藻的光合作用机制提供铁。大肠杆菌具有3种不同类型的铁蛋白，在铁储存和解毒中具有潜在的不同作用，并且是研究铁蛋白功能的模型系统。* 具体目标是：*1。通过定点突变鉴定直接参与铁蛋白储存和释放铁的推定氨基酸残基。将分析重组野生型和变体的晶体结构、铁氧化酶反应动力学、铁矿化和铁释放。2.为了表明铁蛋白在细胞中储存铁，将使用从在不同铁可用性和氧化应激下生长的细胞中分离的天然铁蛋白通过ICP-MS进行金属含量分析。* 3.将通过在生理水平的亚铁螯合代谢物（例如铁蛋白）存在下孵育负载铁的样品来检查铁蛋白的铁释放。组氨酸）和还原剂如黄素和NAPH。将进行筛选以寻找与铁释放有关的蛋白质。这项工作的结果将有助于理解开放海洋中的硅藻水华，并为了解病原体如何科普宿主植物和动物施加的铁限制提供基础。