Identification and characterization of virulence determi

摘要：本项目的目的是鉴定和表征白喉棒状杆菌的毒力决定因素，以了解这种重要的病原体是如何致病的。白喉毒素是白喉隐翅虫的主要毒力决定因素，其表达受铁的调控，很可能是额外的毒力因子与白喉毒素的毒力因子协同调节。在感染期间获得铁的能力是许多细菌病原体致病的关键。本实验室的早期研究表明，hmuO基因是白喉隐翅虫利用血红素和血红蛋白中的铁所必需的。最近的研究主要集中在：1)了解hmuO基因调控的分子机制，2)白喉隐翅虫中涉及血红素运输的因素的特征，3)白喉隐翅虫中更准确地定义各种遗传系统功能的遗传工具的开发，以及4)白喉隐翅虫中DtxR同源基因的特征。HmuO启动子的转录被证明受到双重调控，其中表达受到血红素来源(如血红素或血红蛋白)的正调控，而受白喉毒素抑制蛋白(DtxR)和铁的负调控。本实验室的研究表明，依赖于血红素的hmuO启动子的激活是通过一个两组分的信号转导系统进行的，该系统需要chra和chrS基因，这两个基因分别编码一个反应调节因子和一个传感器激酶。一种ABC(三磷酸腺苷结合盒)型转运系统参与了白喉隐翅虫利用血红素和血红蛋白作为铁源的过程，HmuT脂蛋白被认为是细胞表面的血红素受体。建立了白喉弧菌和溃烂弧菌明确突变的构建系统。 从最近完成的白喉隐翅虫基因组中鉴定出dtxR的同源物mntR。MntR基因被克隆，并被证明是一个五基因操纵子的末端基因，该操纵子还编码一个可能的ABC-金属转运体。MntR产物通过一种依赖于锰的机制调节该操纵子的表达。

Summary: The purpose of this project is to identify and characterize virulence determinants in Corynebacterium diphtheriae in order to understand how this important pathogen causes disease. Expression of diphtheria toxin, the primary virulence determinant of C. diphtheriae, is regulated by iron, and it is likely that additional virulence factors are coordinately regulated with that of the toxin. The ability to acquire iron during an infection is essential for many bacterial pathogens to cause disease. It was shown in earlier studies from this laboratory that the hmuO gene is required for the utilization of iron from heme and hemoglobin in C. diphtheriae. Recent studies have focused on; 1) understanding the molecular mechanisms of hmuO gene regulation, 2) the characterization of factors involved the transport of heme in C. diphtheriae 3) the development of genetic tools in C. diphtheriae to more accurately define the function of various genetic systems and 4)the characterization of a DtxR homolog in C diphtheriae termed MntR. Transcription from the hmuO promoter has been shown to be under dual regulation in which expression is positively regulated by a heme source, such as heme or hemoglobin, and negatively regulated by the diphtheria toxin repressor protein (DtxR) and iron. Studies in this laboratory have shown that heme-dependent activation of the hmuO promoter occurs through a two component signal transduction system that requires the chrA and chrS genes, which encode a response regulator and sensor kinase, respectively. An ABC (ATP-binding cassette) type transport system is involved in the utilization of heme and hemoglobin as iron sources in C. diphtheriae and the HmuT lipoprotein protein is proposed to be the cell surface heme receptor. A system for constructing defined mutation was developed for both C. diphtheriae and C. ulcerans. A homolog of dtxR, mntR, was identified from the recently completed C. diphtheriae genome. The mntR gene was cloned and was shown to be the terminal gene in a five gene operon that also encoded a putative ABC-metal transporter. The product of mntR was shown to regulate expression of this operon by a Mn-dependent mechanism.