Identification and characterization of virulence determi

毒力测定的鉴定和表征

• 批准号: 6678329
• 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/6678329
• 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 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.

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，以了解这种重要病原体是如何引起疾病的。白喉白喉毒素是白喉白喉的主要毒力决定因素，其表达受铁的调控，很可能还有其他毒力因子与白喉白喉毒素协同调控。在感染过程中获取铁的能力对许多细菌病原体致病至关重要。该实验室早期的研究表明，在白喉链球菌中，hmuO基因是利用血红素和血红蛋白中的铁所必需的。最近的研究集中在；1)了解hmuO基因调控的分子机制；2)白喉白喉血红素转运相关因素的表征；3)白喉白喉遗传工具的开发，以更准确地定义各种遗传系统的功能；4)白喉白喉白喉DtxR同源物MntR的表征。hmuO启动子的转录已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，并受到白喉毒素抑制蛋白（DtxR）和铁的负调控。本实验室的研究表明，hmuO启动子的血红素依赖性激活是通过一个双组分信号转导系统发生的，该系统需要chrA和chrS基因，它们分别编码应答调节因子和传感器激酶。白喉白喉对血红素和血红蛋白作为铁源的利用涉及ABC （atp结合盒）型转运系统，HmuT脂蛋白蛋白被认为是细胞表面血红素受体。构建了白喉和溃疡杆菌定义突变的系统。