Role of cardiolipin in Helicobacter pylori flagellar biogenesis

项目总结/摘要 幽门螺杆菌在全世界约一半人口的胃中定植，并且是主要的 是消化性溃疡和慢性胃炎的致病因素，也是胃癌的主要危险因素 和粘膜相关淋巴组织淋巴瘤。H.幽门螺杆菌具有一簇极鞭毛， 用于宿主定植所需的运动性。一个膜鞘包围着H。幽门螺杆菌鞭毛， 这一特征与其他重要的人类病原体，包括致病性弧菌物种共有。提出 鞭毛鞘的功能包括保护鞭毛丝免受胃酸的影响， 宿主细胞在任何细菌物种中，关于鞭毛鞘的合成都是未知的。我们的初步 研究鉴定了在H. pylori的鞭毛生物合成所必需的clsC。pylori G27。高纯度H.幽门 有鞘鞭毛含有大量的CL，证实了ClsC和鞭毛之间的功能联系 鞘这些观察结果导致我们的中心假设，CL是合成H所必需的。幽门 鞭毛鞘，并且CL合成的损伤抑制H. pylori G27。比较 基因组学方法揭示了一些在螺杆菌物种中保守的基因， 有鞘的鞭毛，但在缺乏鞭毛鞘的螺杆菌中不存在。其中一些基因编码 一个外排系统，我们的突变分析表明，所需的鞭毛生物合成在H。pylori G27。 外排系统可以形成一个独特的笼状结构，包围鞭毛马达，破坏其中一个 编码外排系统的基因导致笼状结构的丧失。这些结果导致我们 假设外排系统将CL转运到外膜组装成鞭毛鞘。 了解CL与H. pylori鞭毛鞘，三个具体目标将是 （1）明确合作学习在H中的作用;幽门螺杆菌鞭毛生物发生。(2)为了确定外排系统是否为 参与鞭毛鞘生物合成的CL转运蛋白。(3)确定是否需要CL或外排系统 将蛋白质定位在鞭毛鞘上。这项拟议中的研究将解决我们在这方面的一个关键差距。 对H. pylori鞘鞭毛，以及提供一个范例鞭毛 在其他医学相关细菌中鞘生物合成。这项研究也将对我们的社会产生广泛的影响。 甘油磷脂在细菌细胞包膜中运输的知识。

PROJECT SUMMARY/ABSTRACT Helicobacter pylori colonizes the stomach of about half the human population worldwide and is the major pathogenic factor for peptic ulcer disease and chronic gastritis, as well as a major risk factor for gastric cancer and mucosa-associated lymphoid tissue lymphoma. H. pylori possess a cluster of polar flagella that the cell uses for motility, which is required for host colonization. A membranous sheath surrounds the H. pylori flagellum, a feature shared with other significant human pathogens, including pathogenic Vibrio species. Proposed functions for the flagellar sheath include protection of the flagellar filament from gastric acid and adherence to host cells. Nothing is known about the synthesis of the flagellar sheath in any bacterial species. Our preliminary studies identified an enzyme (ClsC) responsible for synthesis of the glycerophospholipid cardiolipin (CL) in H. pylori, and showed that clsC is required for flagellar biosynthesis in H. pylori G27. Highly purified H. pylori sheathed flagella contain substantial amounts of CL, confirming a functional link between ClsC and the flagellar sheath. These observations lead to our central hypothesis that CL is required for synthesis of the H. pylori flagellar sheath, and lesions in CL synthesis inhibit flagellar biosynthesis in H. pylori G27. A comparative genomics approach revealed a number of genes that are conserved in Helicobacter species that possess sheathed flagella but are absent in Helicobacter species that lack a flagellar sheath. Some of these genes encode an efflux system that our mutational analysis revealed to be required for flagellar biosynthesis in H. pylori G27. The efflux system may form a unique cage-like structure that surrounds the flagellar motor as disrupting one of the genes encoding the efflux system results in loss of the cage-like structure. These results led to our hypothesis that the efflux system transports CL to the outer membrane for assembly into the flagellar sheath. To understand the link between CL and biosynthesis of the H. pylori flagellar sheath, three Specific Aims will be pursued: (1) To define the role of CL in H. pylori flagellum biogenesis. (2) To determine if the efflux system is a CL transporter involved in flagellar sheath biosynthesis. (3) To determine if CL or the efflux system are required for localization of proteins to the flagellar sheath. The proposed research will address a critical gap in our knowledge of the biosynthesis of the H. pylori sheathed flagellum, as well as provide a paradigm for flagellar sheath biosynthesis in other medically relevant bacteria. The research will also have a broad impact on our knowledge of glycerophospholipid trafficking in the bacterial cell envelope.