Role of cardiolipin in Helicobacter pylori flagellar biogenesis

项目摘要/摘要 幽门螺杆菌在全球约一半人口的胃中定植，是主要的 消化性溃疡和慢性胃炎的致病因素，以及胃癌的主要危险因素 和粘膜相关淋巴组织淋巴瘤。幽门螺杆菌拥有一簇极鞭毛，细胞 用于移动性，这是寄主定居所必需的。幽门螺杆菌鞭毛周围有一层膜鞘， 这是其他重要的人类病原体的共同特征，包括致病弧菌物种。建议 鞭毛鞘的功能包括保护鞭毛细丝免受胃酸的影响和粘连 宿主细胞。关于鞭毛鞘在任何细菌物种中的合成，我们一无所知。我们的预赛 研究确定了一种负责合成甘油磷脂(CL)的酶(ClsC)。 幽门螺杆菌G27中鞭毛的生物合成需要ClsC。高纯度幽门螺杆菌 鞘鞭毛含有大量的CL，证实了ClsC与鞭毛之间的功能联系 护套。这些观察结果导致了我们的中心假设，即CL是合成幽门螺杆菌所必需的 鞭毛鞘和CL合成中的损伤抑制Hp G27中鞭毛的生物合成。比较级的 基因组学方法揭示了一些在幽门螺杆菌中保守的基因 有鞘的鞭毛，但在缺乏鞭毛鞘的幽门螺杆菌中没有。其中一些基因编码 我们的突变分析表明，幽门螺杆菌G27中的鞭毛生物合成需要一个外排系统。 外排系统可能形成一种独特的笼状结构，它围绕着鞭毛马达，破坏 编码外排系统的基因导致笼状结构的丢失。这些结果导致我们的 假设外排系统将CL运输到外膜以组装到鞭毛鞘中。 为了了解CL和幽门螺杆菌鞭毛鞘的生物合成之间的联系，将有三个特定的目标 目的：(1)明确CL在幽门螺杆菌鞭毛生物发生中的作用。(2)确定外排系统是否为 CL转运蛋白参与鞭毛鞘的生物合成。(3)确定是否需要CL或外排系统 用于将蛋白质定位到鞭毛鞘。拟议的研究将解决我们在 关于幽门螺杆菌鞘鞭毛生物合成的知识，以及提供鞭毛的范例 在其他医学相关细菌中的鞘生物合成。这项研究也将对我们的 细菌细胞膜中甘油磷脂运输的知识。

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.