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

描述（由申请人提供）：致病菌需要铁来生存和引起感染。血红素占宿主体内可利用铁的90%，在许多细菌病原体的定植和毒力中起着重要作用。志贺氏杆菌和肠侵入性大肠杆菌是导致人类志贺氏菌病的原因，这是一种以结肠粘膜层破坏为特征的疾病。痢疾链球菌的问题尤其严重，因为它会产生一种更严重的疾病，并与危及生命的并发症有关。最近出现的耐药性增加严重限制了现有抗微生物药物的选择。抗菌药物开发策略的转变是将重点放在对细菌生存不是必需的，但对毒性是必需的抗菌靶标上，从而减少了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发病机制的最重要和最清楚的决定因素之一。最近，在许多生物体中，血红素在感染和疾病进展过程中是铁的重要来源。因此，单独靶向血红素摄取和利用或与其他抗菌方法联合可能提供一种新的治疗策略。研究的总体目标是；i)利用位点定向诱变、晶体学和光谱技术的结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；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。这些研究将提供对革兰氏阴性病原体中血红素摄取和利用的分子机制的透彻理解，作为确定未来药物设计和开发的治疗靶点的一步。

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.