Unravelling lipid trafficking for the bacterial outer membrane

项目摘要 细菌外膜是一种脂双层，在抵抗抗生素、洗涤剂和抗生素的过程中起着关键作用。 其他外部压力。尽管对细菌包膜进行了数十年的研究， 磷脂在细菌的内外膜之间通过中间的 周质的亲水空间。我们最近发现，哺乳动物细胞进入（MCE） 蛋白质家族形成结构多样的六聚体环和桶，并且这些蛋白质中的一些可以形成 在内膜和外膜之间形成“桥”或“管道”，以促进脂质转运（Ekiert等人，Cell 2017）。 在未来，我们将努力了解MCE蛋白如何帮助创建跨周质运输 连接内外膜的系统。我们将用冷冻电镜和X射线晶体学来解开 单个成分的结构如何支持其生物功能，以及这些成分如何 组装成更大的内膜、外膜甚至跨膜复合物。我们还将 采用互补的遗传和生物化学方法来测试假设，并探索 MCE系统的运输，包括运输方向，运输活动如何调节，脂质如何 是如何从内外膜中提取并插入内外膜的，以及脂质是如何穿过膜的。 周质这项工作将促进我们对一个基本但知之甚少的方面的理解， 细菌细胞生物学，并可能开辟新的抗生素的发展途径，目标是基本的 外膜生物发生的过程。此外，MCE蛋白的存在，在一些双- 膜细胞器，如叶绿体，表明了解E。coli MCE系统还将具有 对其他细菌衍生细胞器中脂质运输的直接影响。

PROJECT ABSTRACT The bacterial outer membrane is a lipid bilayer that plays a key role in resistance to antibiotics, detergents, and other external stresses. Despite decades of research on the bacterial envelope, it is unknown how phospholipids are trafficked between the bacterial inner and outer membranes, through the intervening hydrophilic space of the periplasm. We recently discovered that members of the mammalian cell entry (MCE) protein family form structurally diverse hexameric rings and barrels, and that some of these proteins may form “bridges” or “pipes” between the inner and outer membrane to facilitate lipid transport (Ekiert, et al. Cell 2017). In the future, we will work to understand how MCE proteins help to create a periplasm-spanning transport system that links the inner and outer membranes. We will use cryo-EM and X-ray crystallography to unravel how the structure of the individual components supports their biological functions, and how these components assemble into larger inner membrane, outer membrane, and even transenvelope complexes. We will also employ complementary genetic and biochemical approaches to test hypotheses and probe the mechanism of trafficking by MCE systems, including the direction of transport, how transport activity is regulated, how lipids are are extracted from and inserted into the inner and outer membranes, and how lipids are transported across the periplasm. This work will advance our understanding of a fundamental yet poorly understood aspect of bacterial cell biology, and may open up avenues to the development of new antibiotics that target the essential process of outer membrane biogenesis. In addition, the presence of MCE proteins in some double- membraned organelles, such as chloroplasts, suggests that understanding E. coli MCE systems will also have direct implications for lipid trafficking in other bacterial-derived organelles.