Understanding phopspholipid homeostasis in Gram-negative bacteria

为了简单起见，所有细胞都可以被认为是化学物质的“袋子”，其中化学物质编码细胞复制所需的材料，以获得和利用营养物质，并基本上在其栖息地内生存。在所有情况下，包含这些化学物质的“袋子”是由称为磷脂的脂肪组成的;“袋子”的正确术语是细胞膜。不同的生物体具有不同的细胞膜特性。一些最危险的细菌有两层细胞膜，简单地称为内膜和外膜。外膜上布满了蛋白质，这些蛋白质在膜上形成了门控孔，允许水和营养物质流入细胞，并将废物排出细胞。这些细菌的外膜也被一种叫做脂多糖的非常特殊的脂质所修饰，这种脂质使细菌的外膜非常坚固，使细菌能够抵抗许多抗生素。通过了解细菌如何形成外膜，并用蛋白质和脂多糖修饰它，我们可以开发出杀死细菌或阻止细菌生长的药物。几年来，我们和其他小组一直在研究蛋白质和脂多糖是如何被整合到外膜中的。然而，到目前为止，还没有人弄清楚细胞内化学物质产生的磷脂是如何穿过内膜进入外膜的。找出这是如何发生的是非常重要的;如果我们能弄清楚这些磷脂是如何被运输到外膜的，那么我们就可以开发出阻止这一过程的药物，最终杀死细菌。幸运的是，我们最近在外膜中发现了一种蛋白质，它可以结合其中一种磷脂。我们有很好的证据表明，这种蛋白质接收磷脂进入外膜，如果你阻止这种蛋白质发挥作用，细菌就会对抗生素非常敏感。我们已经证明，缺乏这种蛋白质的细菌无法引起疾病，有趣的是，这种蛋白质可以安全有效地用于疫苗中，以帮助身体对抗细菌感染。这是第一次有人发现具有这种活性的蛋白质。因此，这个项目的总体目标是确定细菌如何识别和组织脂质进入它们的外膜。我们将用许多不同的方法来解决这个问题。我们将研究这种蛋白质是否能够识别外膜内发现的所有不同脂质。我们将研究蛋白质是否将脂质组织到外膜内的特定位置，这可能对外膜抵抗抗生素很重要。我们将研究这种蛋白质是否需要伴侣蛋白才能有效地发挥作用。我们将使用许多不同的技术来解决这个问题，包括遗传学，生物化学和结构生物学，我们阐明蛋白质的三维结构。最终，该项目将揭示许多研究人员一直在寻找的途径，并将使行业开始利用这些知识来阻止或预防感染。

For simplicity, all cells can be considered 'bags' of chemicals, where the chemicals encode the material required for the cell to replicate, to obtain and utilise nutrients, and essentially survive within its habitat. In all cases, the 'bag' that contains these chemicals is made up of fats called phospholipids; the correct term for the 'bag' is the cell membrane. Different organisms have different cell membrane properties. Some of the most dangerous bacteria have two cell membranes, simply termed an inner and an outer membrane. The outer membranes are studded with proteins which form gated holes in the membrane to allow water and nutrients to flow into the cell and waste products to be pushed out of the cell. The outer membranes of these bacteria are also decorated with a very specialised lipid called lipopolysaccharide that makes the membrane very strong and allows the bacteria to resist many antibiotics.By understanding how bacteria make their outer membranes, and decorate it with proteins and lipopolysaccharide we can develop drugs that will either kill the bacteria or prevent it from growing. For several years we and other groups have study how the proteins and lipopolysaccharide is incorporated into the outer membrane. However, to date nobody has figured out how phospholipid, which is made by the chemicals inside the cell, can make its way across the inner membrane and into the outer membrane. Finding out how this happens is extremely important; if we can figure out how these phospholipids are trafficked to the outer membrane then we may be able to develop drugs that stop this process, ultimately killing the bacteria.Fortunately, we have recently found a protein in the outer membrane that binds one of the phospholipids. We have good evidence that this protein receives phospholipid into the outer membrane and if you stop this protein from functioning the bacteria become very sensitive to antibiotics. We have shown that bacteria that lack this protein are unable to cause disease and interestingly this protein can be used safely and effectively in vaccines to help the body fight bacterial infections. This is the first time anyone has found a protein with such activity. Therefore, the overall aim of this project is to determine how bacteria recognize and organize lipids into their outer membrane.We will tackle this problem in a number of different ways. We will investigate whether the protein is capable of recognising all of the different lipids found within the outer membrane. We will investigate if the protein organizes the lipids into specific places within the outer membrane that might be important for the outer membrane in resisting antibiotics. We will investigate if this protein requires partner proteins to be effective at its job. We will use many different techniques to address this problem including genetics, biochemistry and structural biology where we elucidate the 3-dimensional structures of proteins. Ultimately, this project will shed light on a pathway that many researchers have been looking for and it will allow industry to begin to exploit this knowledge to stop or prevent infections.