Bacterial anaerobic iron homeostasis

 描述（由申请人提供）：铁是几乎所有生物体的必需营养素，因为它是许多蛋白质的辅因子，通常以铁、血红素或铁硫（Fe-S）簇的形式存在。然而，铁在环境中通常是稀缺的，将其获取和使用置于生物学中一些最高度调控的途径的控制之下。我们正在研究兼性厌氧菌大肠杆菌中铁代谢的两个关键调节因子，IscR和Fur。我们发现，在厌氧条件下，由IscR和Fur转录的活性和基因发生显著变化。因此，该项目旨在了解这种变化是如何发生的，以及它如何影响厌氧条件下铁的利用。我们的第一个目标是了解在厌氧条件下，这种细菌和其他细菌中铁稳态的全球调节剂Fur的活性如何调节。我们将确定在厌氧条件下游离铁的增加是否可以解释在无氧条件下选择弱亲和力启动子时Fur活性的增加。我们发现，IscR是一种新的DNA结合蛋白，它可以识别载脂蛋白和[2Fe-2S]结合形式的不同序列基序。该提案的第二个目标是定义IscR的生物化学和结构特性，其允许金属结合在厌氧条件下改变其DNA结合特异性。在这段时间里，我们 将扩展我们的研究Fur和IscR从研究良好的K12实验室E。大肠杆菌菌株与临床相关的尿路致病性E. coliCFT073。尿路致病性大肠杆菌是尿路感染的主要原因，模型系统中的研究已将Fur和IscR与该菌株的发病机制联系起来。我们的研究结果将提供重要的新的见解，如何在厌氧条件下的Fur和IscR的功能被改变。此外，了解这些调节剂的活性是如何协调控制铁和Fe-S稳态的，将使我们能够开发新的策略来控制宿主厌氧环境中真菌和病原微生物的生长。

 DESCRIPTION (provided by applicant): Iron is an essential nutrient for nearly all organisms because it serves as a co-factor for many proteins, often in the form of iron, heme or iron-sulfur (Fe-S) clusters. Yet iron is often scarce in the environment placing its acquisition and usage under control of some of the most highly regulated pathways in biology. We are studying two key regulators of iron metabolism in the facultative anaerobe Escherichia coli, IscR and Fur. We have found that the activity and genes that are transcribed by IscR and Fur change significantly under anaerobic conditions. Thus, this project seeks to understand how this change occurs and how it impacts the utilization of iron under anaerobic conditions. Our first goal is to understand how activity of Fur, the global regulator of iron homeostasis in this and other bacteria, is regulated under anaerobic conditions. We will determine if an increase in free iron under anaerobic conditions can explain the increased activity of Fur at select weak affinity promoters in the absence of oxygen. We discovered that IscR is a novel DNA-binding protein that recognizes different sequence motifs in its apo- and [2Fe-2S]-bound forms. A second goal of this proposal is to define the biochemical and structural properties of IscR that allow metal binding to alter its DNA-binding specificity under anaerobic conditions. In this funding period, we will extend our studies of Fur and IscR from the well-studied K12 laboratory E. coli strain to the clinically relevant uropathogenic E. coli CFT073. Uropathogenic E.coli is a major cause of urinary tract infections and studies in model systems have linked both Fur and IscR to pathogenesis by this strain. Our results will provide important new insight as to how function of Fur and IscR are altered under anaerobic conditions. In addition, understanding how the activity of these regulators are coordinated to control iron and Fe-S homeostasis will allow us to develop new strategies to control the growth of commensal and pathogenic microbes in the anaerobic environment of the host.