Iron Acquisition in Anthrax

描述(申请人提供)：细菌病原体必须获得铁才能在哺乳动物宿主中复制和生存。铁-卟啉血红素与循环中的血红蛋白结合，含有高达80%的体内铁。这一事实导致了有实验证据支持的假设，即在感染期间，血红素是铁的来源。然而，在炭疽杆菌中，铁调节表面决定基因(ISD)的缺失并没有降低动物感染模型中炭疽杆菌的毒力。ISD基因编码与血红素结合的表面蛋白。这些结果表明，其他因素也有助于这种致命病原体的铁摄取。ISD系统的一个特点是存在一个被称为近铁转运蛋白(NEAT)结构域的保守蛋白质模块，它介导血红素向革兰氏阳性病原菌的转移。在对炭疽杆菌基因组的电子分析中，表明一个非ISD基因，命名为BAS0520，被注释为编码单一的整合域蛋白。这项建议的目的是确定BAS0520是否代表炭疽感染过程中介导血红素吸收的“缺失环节”。具体地说，我们假设BAS0520是一种表面蛋白，它从宿主血红蛋白中提取血红素，从而促进血红素向细菌细胞的运输，并增强哺乳动物宿主中依赖铁的复制。这一假设将以两个目的进行检验：1.确定BAS0520的机械功能。生化方法将确定BAS0520的整合域的分子和结构因素。2.确定BAS0520在铁获取和炭疽病中的作用。使用全毒力菌株的生长研究和动物感染模型将被用来确定哪些铁吸收机制对炭疽病是重要的。 公共卫生相关性：细菌病原体需要铁才能复制。这项提议的目标是了解炭疽杆菌是如何在感染期间获得铁的，炭疽杆菌是一种潜在的生物恐怖主义武器，也是炭疽病的病原体。了解细菌是如何在哺乳动物宿主体内生存、生长和传播的，将有助于发现药物开发的新靶点。

DESCRIPTION (provided by applicant): Bacterial pathogens must acquire iron to replicate and survive in mammalian hosts. The iron-porphyrin heme, bound to circulating hemoglobin, contains up to 80% of bodily iron. This fact has led to the hypothesis, which is backed by experimental evidence, that heme serves as a source of iron during infection. However, in the anthrax-causing bacteria B. anthracis, deletion of iron-regulated surface determinant (Isd) genes, which code for surface proteins that bind heme, did not reduce B. anthracis virulence in animal models of infection. These results suggest other factors contribute to iron uptake in this deadly pathogen. A hallmark of Isd systems is the presence of a conserved protein module termed the near-iron transporter (NEAT) domain, which mediates the transfer of heme into Gram-positive pathogenic bacteria. In silico analysis of the genome of B. anthracis indicates a non-Isd gene, designated BAS0520, is annotated to encode for a single NEAT-domain protein. The objective of this proposal is to determine if BAS0520 represents the "missing link" mediating heme uptake during anthrax infection. Specifically, we hypothesize BAS0520 is a surface protein that extracts heme from host hemoglobin, thereby promoting heme transport into the bacterial cell and enhancing iron-dependent replication in mammalian hosts. This hypothesis will be tested with two aims: 1. Determine the mechanistic function of BAS0520. Biochemical approaches will define the molecular and structural factors of the NEAT domain of BAS0520. 2. Determine the role of BAS0520 in iron acquisition and anthrax disease. Growth studies and animal infection models using fully virulent strains will be used to define which mechanisms of iron uptake are important for anthrax disease. PUBLIC HEALTH RELEVANCE: Bacterial pathogens require iron in order to replicate. The goal of this proposal is to understand how B. anthracis, a potential weapon of bioterrorism and the causative agent of anthrax disease, acquires iron during infection. Understanding how bacteria survive, grow, and spread inside mammalian hosts will lead to the discovery of new targets for drug development.