Structural And Biochemical Characterization Of A Novel Mycobacterial Heme Uptake

结核病（TB）继续在世界各地夺走数百万人的生命。新的工具来 预防和治疗这种疾病是迫切需要的。铁是一种重要的金属， 生命形式和大多数细菌病原体，包括分枝杆菌，必须从 它的宿主才能生存因此，铁的获取途径在分枝杆菌中得到了很好的研究， 它们的组分对分枝杆菌的生存力是必需的。到目前为止，人们认为铁 在分枝杆菌中的摄取是由能够去除铁的分枝杆菌素协调的 转铁蛋白然而，在人类中，转铁蛋白铁占不到1% 血红素铁占人体总铁的80%以上。因此一个 可以推测分枝杆菌能够从人类血红素中获得铁 源最近的研究，重点是分枝杆菌素缺陷突变体， 结核分枝杆菌（Mtb）和卡介苗，表明有一个新的血红素 获得途径。有趣的是，BCG有一个减弱的血红素 与结核分枝杆菌相比，此外，Mtb蛋白质组范围的方法 在我们的实验室进行，以确定潜在的蛋白质参与血红素 采集我们提出了一个假定的途径，血红素是螯合从人类 血红蛋白通过分泌的血细胞，通过血红素跨膜转移 转运蛋白，并打破了细胞溶质血红素降解蛋白释放铁。 这项研究将有助于阐明血红素从人体转移的分子机制 细菌。此外，我们还将研究每个基因在这一提议中的作用。 途径，在体内对分枝杆菌血红素摄取有影响。 这项建议的具体目标如下： 1)新型分枝杆菌血团的生物物理和生物化学研究。 2)探讨血红素从宿主血红蛋白转移到血细胞的机制， 血红素转运蛋白 3)血红素摄取相关蛋白质的鉴定与表征。 4)结核分枝杆菌血红素摄取系统的研究。 我建议的研究重点是全面了解这部小说 分子（单蛋白）和细胞上的分枝杆菌血红素摄取系统 程度.有趣的是，大多数参与这一途径的蛋白质没有密切的非- 分枝杆菌，蛋白质序列同源物，此外，血细胞具有新的 三维褶皱考虑到这一点，血红素摄取途径提供了一些 很好的蛋白质靶点，用于开发抗结核病的治疗方法。

Tuberculosis (TB) continues to kill millions of people around the world. New tools to prevent and treat this disease are urgently needed. Iron is an essential metal for all forms of life and most bacterial pathogens including mycobacteria must import iron from its host to survive. Hence iron acquisition pathways are well studied in mycobacteria as their components are essential to mycobacterial viability. Thus far, it is thought that iron uptake in mycobacteria is orchestrated by mycobactins that are capable of removing iron from human transferrin. However in humans, transferrin iron accounts for less than 1% of the body's total iron whereas heme iron can represent greater than 80%. Thus one may speculate that mycobacteria are capable of acquiring iron from human heme sources. Recent studies, which focus on mycobactin deficient mutants of Mycobacterium tuberculosis (Mtb) and BCG, suggest that there is a novel heme acquisition pathway in mycobacteria. Interestingly, BCG has an attenuated heme uptake pathway compared to Mtb. In addition, an Mtb proteome-wide approach has been undertaken in our laboratory to identify potential proteins involved in heme acquisition. We propose a putative pathway where heme is sequestered from human hemoglobin by a secreted hemophore, transferred across the membrane by heme transporters, and broken-down by cytosolic heme-degrading protein to release iron. This research will shed light on the molecular mechanism of heme transfer from humans to bacteria. In addition, we will investigate the affect each gene within this proposed pathway, has on mycobacterial heme uptake in vivo. The specific aims of this proposal are as follows: 1) Biophysical and biochemical investigation of the novel mycobacterial hemophore. 2) Explore the mechanism of heme transfer from host hemoglobin to hemophore to heme transporter. 3) Identification and characterization of other proteins involved in heme uptake. 4) Investigation into mycobacterial heme uptake system in Mtb. My proposed research focuses on gaining a comprehensive understanding of this novel mycobacterial heme uptake system on both molecular (single protein) and cellular levels. Interestingly, most of the proteins involved in this pathway have no close non- mycobacterial, protein sequence homologs, and additionally, the hemophore has a novel three-dimensional fold. With this in mind, the heme uptake pathway provides a number of good protein targets for the development of therapeutics against TB.