POTRA domain structure and function by NMR spectroscopy

本课题将采用光谱学方法对革兰氏阴性菌外膜蛋白的三维结构和生化功能进行分析。这种蛋白质被称为自转运蛋白。它们负责将物质分泌出细菌细胞并进入外膜和周围环境。在这里，我们关注的是这些蛋白质的一个组成部分，称为POTRA结构域，它被认为是负责招募细菌蛋白质用于分泌的。革兰氏阴性菌的特征是外膜包围着一个被称为肽聚糖的聚合网络。外膜的主要功能是在肽聚糖周围形成半透层，保护细菌细胞。蛋白质被插入外膜以控制其渗透性。对许多细菌基因组的分析表明，含有POTRA结构域的自转运蛋白普遍存在于革兰氏阴性菌的外膜中，对其生存至关重要。事实上，该系统是所有革兰氏阴性菌中使用最广泛的蛋白质分泌系统。含有POTRA结构域的自转运体是形成细菌外膜和正确插入蛋白质所必需的。一些插入致病菌外膜的蛋白质是重要的抗原，作为保护性免疫反应的靶标。了解POTRA结构域如何识别和组装这些蛋白质对于靶向致病菌和在细菌感染期间操纵免疫反应非常重要。不同类型革兰氏阴性菌的外膜除含有蛋白质外，还含有多种脂质。外小叶由脂多糖、糖脂和磷脂组成，不同的细菌种类不同。外膜中的脂质类型对于蛋白质组装到膜中至关重要，并且在免疫反应中也具有重要作用。因此，我们还将研究脂质和膜对POTRA结构域的作用，POTRA结构域存在于膜旁边，帮助蛋白质进入和穿过膜，以便更好地了解POTRA结构域在膜表面的定向和活性。

In this research project, the three dimensional structures and biochemical functions of proteins found in the outer membrane of Gram-negative bacteria will be analyzed by spectroscopic methods. The proteins are known as autotransporters. They are responsible for the secretion of materials out of the bacterial cell and into the outer membrane and surrounding environment. Here we focus on a component of these proteins called the POTRA domain which is thought to be responsible for recruiting bacterial proteins for secretion. Gram negative bacteria are characterized by an outer membrane that surrounds a polymeric network known as peptidoglycan. The main function of the outer membrane is to form a semi-permeable layer around the peptidoglycan to protect the bacterial cell. Proteins are inserted into the outer membrane in order to control its permeability. The analysis of many bacterial genomes has revealed that POTRA domain-containing autotransporters are universally found in outer membranes of Gram negative bacteria, and are essential for their survival. In fact, this system is the most widely used protein secretion system within all Gram-negative bacteria. The POTRA domain-containing autotransporters are needed to form bacterial outer membranes and to insert proteins correctly. Some of the proteins inserted into the outer membrane of pathogenic bacteria are important antigens that act as targets of protective immune responses. Understanding how the POTRA domain recognizes and assembles these proteins is important for targeting pathogenic bacteria and for manipulating the immune response during a bacterial infection. The outer membranes of different types of Gram-negative bacteria contain a variety of lipids in addition to proteins. The outer leaflet is composed of lipopolysaccharides, glycolipids and phospholipids which differ between bacterial species. The type of lipid in the outer membrane is essential for the assembly of proteins into the membrane, and also have important roles in immune response. Consequently, we will also investigate the role of the lipids and membrane on POTRA domains, which exist next to the membrane and help to usher proteins into and through the membrane, in order to better understand how POTRA domains are oriented and active at the membrane surface.