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助因子，通常以铁、血红素或铁硫 (Fe-S) 簇的形式存在。然而，铁在环境中往往很稀缺，使其获取和使用受到生物学中一些最严格监管的途径的控制。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IscR和Fur转录的活性和基因在厌氧条件下发生显着变化。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。我们的首要目标是了解毛皮（这种细菌和其他细菌中铁稳态的全局调节剂）的活性在厌氧条件下是如何受到调节的。我们将确定厌氧条件下游离铁的增加是否可以解释在无氧条件下选定的弱亲和力促进剂上毛皮活性的增加。我们发现 IscR 是一种新型 DNA 结合蛋白，可识别 apo 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 的生化和结构特性，允许金属结合在厌氧条件下改变其 DNA 结合特异性。在本次资助期间，我们 将把我们对 Fur 和 IscR 的研究从经过充分研究的 K12 实验室大肠杆菌菌株扩展到临床相关的尿路致病性大肠杆菌 CFT073。尿路致病性大肠杆菌是尿路感染的主要原因，模型系统的研究已将 Fur 和 IscR 与该菌株的发病机制联系起来。我们的结果将为 Fur 和 IscR 的功能在厌氧条件下如何改变提供重要的新见解。此外，了解这些调节因子的活性如何协调以控制铁和 Fe-S 稳态将使我们能够制定新策略来控制宿主厌氧环境中共生微生物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.