Structure-Function of the Shigella dysenteriae heme uptake operon (shu)

描述（由申请方提供）：病原菌需要铁才能存活并引起感染。血红素占宿主体内可利用铁的90%，在许多细菌病原体的定殖和毒力中起重要作用。志贺菌和肠侵袭性E.大肠杆菌是导致人类志贺氏菌病的原因，志贺氏菌病是一种以结肠粘膜层破坏为特征的疾病。S.大肠杆菌是特别成问题的，因为它产生更严重的疾病形式，并与危及生命的并发症有关。最近出现的耐药性的增加严重限制了可用的抗微生物剂的选择。抗菌药物开发策略的转变一直是关注对细菌存活不必要但对毒力必需的抗菌靶标，从而减少耐药性发展的选择压力。从宿主获得铁的能力是细菌毒力和致病性的最重要和最好理解的决定因素之一。最近，在许多生物体中已经表明，血红素是感染和疾病进展过程中铁的重要来源。因此，单独或与其他抗微生物方法组合靶向血红素摄取和利用可能提供新的治疗策略。研究的总体目标是：i）利用定点诱变、晶体学和光谱技术的组合来表征血红素摄取蛋白，以确定血红素摄取系统的血红素结合特性。ii）利用蛋白脂质体中的体外模型系统确定血红素通过细菌外膜转运到细胞质的机制;以及iii）通过蛋白质组学和代谢组学研究确定细胞质血红素结合蛋白ShuS在细胞内血红素代谢中的作用。这些研究将提供一个彻底的了解血红素的摄取和利用的分子机制，在革兰氏阴性病原体作为一个步骤，以确定未来的药物设计和开发的治疗目标。 公共卫生相关性：考虑到对当前抗生素的耐药性增加，对靶向肠道病原体如志贺氏菌的新疗法的需求是高度优先的。S.志贺氏菌病的病原体，每年造成1.6亿起疫情，在发展中国家发病率和死亡率很高。在每年估计的110万例死亡中，60%发生在5岁以下的儿童中。S.该菌的毒力和血红素的吸收和代谢特性可能为药物开发提供新的治疗靶点。

DESCRIPTION (provided by applicant): Pathogenic bacteria require iron for their survival and ability to cause infection. Heme comprises 90% of the iron available within the host and plays a significant role in the colonization and virulence of many bacterial pathogens. Shigella spp. and enteroinvasive E. coli are responsible for shigellosis in humans, a disease characterized by the destruction of the mucosal layers of the colon. S. dysenteriae is particularly problematic as it produces a more severe form of the disease and is associated with life threatening complications. The recent increase in the emergence of drug resistance has severely limited the choice of antimicrobial agents available. A shift in strategy for antimicrobial development has been to focus on antimicrobial targets that are not essential for bacterial survival, but are required for virulence, thus reducing the selective pressure for development of drug resistance. The ability to acquire iron from the host is one of the most important and well understood determinants of bacterial virulence and pathogenesis. Recently it has been shown in a number of organisms that heme is an essential source of iron during infection and disease progression. Therefore, targeting heme uptake and utilization alone or in combination with other antimicrobial approaches may provide a novel therapeutic strategy. The overall goal of the studies are; i) To characterize the heme uptake proteins utilizing a combination of site-directed mutagenesis, crystallographic and spectroscopic techniques to determine heme binding properties of the heme uptake system. ii) To determine the mechanism of heme transport through the bacterial outer membrane to the cytoplasm utilizing in vitro model systems in proteoliposomes; and iii) to determine the role of the cytoplasmic heme binding protein ShuS in intracellular heme metabolism through proteomic and metabolomic studies. These studies will provide a thorough understanding of the molecular mechanisms of heme uptake and utilization in gram-negative pathogens as a step toward identifying therapeutic targets for future drug design and development. PUBLIC HEALTH RELEVANCE: The need for new therapeutics targeting enteric pathogens such as Shigella dysenteria is a high priority given the increase in resistance to current antibiotics. S. dysenteriae the causative agent of shigellosis, is responsible for 160 million outbreaks per year and has a high rate of morbidity and mortality in developing countries. Of the estimated 1.1 million deaths per year 60% occur in children under the age of 5 years. Heme utilization by S. dysenteriae is required for virulence and characterization of heme uptake and metabolism may provide novel therapeutic targets for drug development.