Regulation of outer membrane biogenesis components LptD and Omp85 in cyanobacteria Anabaena sp. PCC 7120

蓝藻是一种光自养细菌，除了质膜和肽聚糖层外，还被外膜包围。这种高功能膜的生物发生是一个复杂的现象，涉及不同的外膜特定脂类和外膜蛋白的组装机制。参与这一过程的主要外膜定位因子是多肽转运β-桶蛋白家族的蛋白和类脂A输出蛋白。在蓝藻中发现的这两个蛋白质家族在系统发育上与各自参与叶绿体生物发生的机制有关。我们的目的是了解蓝藻鱼腥藻外膜生物发生的这些基本因子的功能和相互作用。PCC7120作为蓝藻模型系统。我们将探索这三个已鉴定的Omp85蛋白的功能多样性。这包括底物定义以及对这三种蛋白质形成的复合体的分析。同时，我们将分析脂类A转运系统的复杂结构以及脂类分子跨周质转运的功能模式。这些结果将使我们了解外膜的功能模式，这对细胞的生存非常重要，因为它形成了对环境的外部屏障。此外，我们的结果将使我们对叶绿体中蛋白质的功能做出结论，叶绿体的外膜含有两个蛋白质家族，具有蛋白质和脂类运输的功能。

Cyanobacteria are photoautotrophic bacteria surrounded by an outer membrane in addition to the plasma membrane and the peptidoglycan layer. The biogenesis of this highly functional membrane is a complex phenomenon involving distinct machineries for the assembly of the outer membrane specific lipids and outer membrane proteins. The major outer membrane localized factors involved in this process are proteins of the polypeptide-transporting beta-barrel family and proteins for lipid A export. Both protein families found in cyanobacteria are phylogenetically related to the respective machineries involved in chloroplast biogenesis. We aim to understand the function and the interplay of these essential factors for outer membrane biogenesis in the cyanobacterium Anabaena sp. PCC 7120 as a cyanobacterial model system. We will explore the functional diversity of the three identified Omp85 proteins. This includes substrate definition as well as the analysis of the complexes formed by these three proteins. In parallel, we will analyze the complex architecture of the lipid A transport system as well as the functional mode of the transfer of the lipid molecule across the periplasm. The results will yield an understanding of the functional mode of the outer membrane, which is important for cell survival as it forms the outer barrier to the environment. In addition, our results will allow conclusions on the function of the proteins in chloroplasts, which contain both protein families in their outer membrane with function in protein and lipid transport.