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

描述(申请人提供)：病原菌需要铁才能生存和引起感染。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方面发挥着重要作用。志贺氏菌属肠道侵袭性大肠杆菌是人类志贺氏菌病的罪魁祸首，志贺氏菌病是一种以结肠粘膜层破坏为特征的疾病。痢疾杆菌的问题尤其严重，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菌剂的选择。抗菌素开发战略的转变是将重点放在对细菌生存不是必不可少的、但对毒力来说是必需的抗菌素靶标上，从而减少发展耐药性的选择压力。从宿主获取铁的能力是细菌毒力和致病机制最重要和最广为人知的决定因素之一。最近，在一些生物体中已经表明，在感染和疾病进展过程中，血红素是铁的重要来源。因此，单独针对血红素的吸收和利用或与其他抗菌方法联合使用可能提供一种新的治疗策略。这些研究的总体目标是：i)利用定点突变、结晶学和光谱技术相结合的方法来表征血红素吸收蛋白，以确定血红素吸收系统的血红素结合特性。Ii)利用蛋白质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；以及iii)通过蛋白质组学和代谢组学研究，确定细胞质中的血红素结合蛋白SHU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吸收和利用的分子机制的透彻了解，从而为未来的药物设计和开发确定治疗靶点。 公共卫生相关性：鉴于当前抗生素耐药性的增加，针对志贺氏菌痢疾等肠道病原体的新疗法的需要是高度优先的。痢疾杆菌是志贺氏菌病的病原体，每年造成1.6亿起疫情，在发展中国家具有很高的发病率和死亡率。据估计，每年有110万人死亡，其中60%发生在5岁以下儿童。痢疾链球菌对血红素的利用是致病所必需的，对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.