Characterization of C. diptheria virulence determinants

白喉棒状杆菌毒力决定因素的表征

• 批准号: 6543474
• 负责人: MICHAEL P SCHMITT
• 金额: --
• 依托单位国家: 美国
• 资助国家: 美国
• 起止时间: 至
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/6543474
• 关键词: Corynebacterium; Corynebacterium diphtheriae; bacterial cytopathogenic effect; bacterial genetics; bacterial proteins; biological signal transduction; biological transport; diphtheria toxin; gene expression; genetic regulation; heme; heme oxygenase; hemoglobin; host organism interaction; intermolecular interaction; iron; iron metabolism; microorganism metabolism; molecular cloning; nonblood lipoprotein; nucleic acid sequence; protein kinase; protein structure function; species difference; virulence

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 and 3) the development of genetic tools in C. diphtheriae to more accurately define the function of various genetic systems. 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 related pathogen C. ulcerans. The three proteins identified in this system are homologous to proteins involved in heme transport from gram-negative bacteria. The HmuT protein, which is a lipoprotein, is proposed to be the cell surface receptor for heme. A system for constructing defined mutation was developed for both C. diphtheriae and C. ulcerans. Mutations in the gene encoding the heme receptor, hmuT, were constructed in both Corynebacterium species. Disruption of the hmuT gene in C. ulcerans resulted in an inability to use heme as an iron source, while inactivation of hmuT in C. diphtheriae had no effect on heme transport, suggesting this species has an additional mechanism for transporting heme. The heme transport locus from C. ulcerans was also cloned and sequenced and was shown to be approximately 70-80 homologous to the heme transport locus from C. diphtheriae.

总结：该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如何引起疾病。白喉毒素是C.白喉毒素受铁的调节，并且其他毒力因子很可能与毒素的毒力因子协同调节。 在感染期间获得铁的能力对于许多细菌病原体引起疾病是必不可少的。 本实验室的早期研究表明，在C.白喉 最近的研究集中在：1）了解hmuO基因调控的分子机制，2）在C.白喉的遗传工具的发展。白喉，以更准确地定义各种遗传系统的功能。 已显示来自hmuO启动子的转录处于双重调节下，其中表达由血红素源（诸如血红素或血红蛋白）正调节，并且由白喉毒素阻遏蛋白（DtxR）和铁负调节。 本实验室的研究表明，血红素依赖性激活的hmuO启动子发生通过两个组件的信号转导系统，需要chrA和chrS基因，分别编码一个响应调节和传感器激酶。ABC（ATP结合盒）型转运系统参与了C.白喉及相关病原C.溃疡。 在该系统中鉴定的三种蛋白质与革兰氏阴性细菌中参与血红素运输的蛋白质同源。 HmuT蛋白是一种脂蛋白，被认为是血红素的细胞表面受体。建立了一个针对两种C.白喉和C.溃疡。 在编码血红素受体hmuT的基因中的突变在两个棒状杆菌属物种中构建。在C.溃疡病导致不能使用血红素作为铁源，而在C.白喉对血红素转运没有影响，表明该物种具有转运血红素的额外机制。 从C. ulcerans的血红素转运基因座的同源性为70-80。白喉