Structure and mechanism of the Mla lipid transport system in the multidrug-resistant bacterium A. baumannii

近年来，我们观察到“超级细菌”的急剧增加，这些细菌对所有已知的抗生素都有抗药性。这在医院环境中是一个特别重要的担忧，超级细菌会导致接受常规医疗程序的患者无法治疗的感染。每年有超过20，000人死于超级细菌感染。在许多细菌中，这种抗药性是由其表面的厚脂质（外膜）引起的。这种膜作为物理屏障，阻止许多药物进入细菌细胞。这种外膜的脂质组成是非常具体的调节，因为它是其物理完整性的关键。然而，细菌将脂质转运到外膜和从外膜转运脂质的机制仍然知之甚少。最近，一组被称为Mla系统（用于维持脂质不对称）的蛋白质被证明是维持完整外膜所必需的。该项目的目的是表征该系统的脂质转运的分子基础。具体来说，我们将研究来自鲍氏不动杆菌的Mla系统，鲍氏不动杆菌是一种已知的多重耐药细菌，导致全球高达20%的耐药感染。我们将研究不同的Mla蛋白如何相互作用，以及它们如何招募和转运脂质。特别是，我们将利用高分辨率电子显微镜的最新进展，在原子水平上表征这些蛋白质，这将使我们能够了解Mla系统的蛋白质如何识别脂质并将其转运到外膜和/或从外膜转运。最终，这可以用于开发预防抗生素耐药性的疗法。

In recent years, we have observed a dramatic increase in "superbugs", bacteria that are resistant to all known antibiotics. This is a particularly important worry in hospital settings, where superbugs cause untreatable infections in patients undergoing routine medical procedures. More than 20,000 people die from superbug infections every year.In many bacteria, this drug resistance is caused by a thick lipid later (the outer membrane) on their surface. This membrane acts as a physical barrier, preventing many drugs from entering the bacterial cell. The lipid composition of this outer membrane is very specifically regulated, as it is critical for its physical integrity. However, the mechanisms used by bacteria to transport lipids to and from the outer membrane are still poorly understood.Recently, a set of proteins termed the Mla system (for Maintenance of Lipid Asymmetry) was shown to be essential to maintain an intact outer membrane. The aim of this project is to characterize the molecular basis for lipid transport by this system. Specifically, we will study the Mla system from the bacterium Acinetobacter baumannii, a known multi-drug resistant bacterium responsible for up to 20% of antibiotic-resistant infections world-wide.We will study how the different Mla proteins interact with each other, and how they recruit and transport lipids. In particular, we will exploit the latest advances in high-resolution electron microscopy to characterize these proteins at the atomic level.This will allow us to understand how the proteins from the Mla system recognize lipids and transport them to and/or from the outer membrane. Ultimately, this could be exploited for the development of therapeutics that prevent antibiotics resistance.