Understanding an ancient universal membrane effector system

所有活着的细胞都被一层薄膜包围，使细胞内部与外部环境分开。这一重要的细胞边界层含有蛋白质，使细胞能够摄取食物并排出废物。膜也被通电，这意味着细胞主动地产生和维持跨膜的离子梯度和电压。这种所谓的电化学梯度是细胞储存能量的关键方法之一，可以用来推动营养物质的吸收和排出废物。此外，电化学梯度对于ATP的合成是至关重要的，ATP是一种用于为细胞内过程提供能量的关键分子。因此，膜的完整性对活细胞的正常功能至关重要，许多已知的毒素，包括一些抗生素，都是通过破坏膜来发挥作用的。在细胞的早期进化过程中，一种名为IM30的蛋白质进化而来，这种蛋白质在破坏剂存在的情况下具有保护细胞膜的作用。这些蛋白质是在30多年前发现的，它们被发现采用环状结构，可以相互堆积形成管状结构。此外，众所周知，当细胞膜受损时，这些蛋白质会在细胞内积累到非常高的水平，并直接与细胞膜结合。然而，它们如何保护膜，使电化学电位保持不变，目前尚不清楚。在这个项目中，我们组建了一支不同的研究团队，他们处于职业生涯的不同阶段，拥有不同的专业知识。我们都有兴趣试图弄清楚IM30蛋白是如何保护细胞膜的。他们可能通过形成覆盖在细胞膜内部的涂层，通过形成包裹细胞并将细胞膜结合在一起的‘肋骨’，或者通过允许细胞膜形成小碎片来带走破坏细胞的毒素，来实现这一点。或者，他们可能会专门投射产生电化学势的蛋白质，或者利用它来制造ATP。目前，我们根本不知道。然而，无论机制是什么，它都将是一种全新的机制，并告诉我们关于生物膜如何组织和功能的重要基本信息。为了弄清楚这些蛋白质是如何发挥作用的，我们将使用大量不同的微生物物种，因为这些微生物代表了相对简单的细胞，我们可以有效地研究这些细胞，而且我们知道IM30在哪里是重要的。我们将系统地表征不同细胞含有多少蛋白质，蛋白质在细胞中的定位，它们是否在细胞内组装成环和棒，以及它们的功能如何受到其他因素的调节。我们将开发新的技术来实时测量活细胞中的电化学梯度，这将为我们提供必要的工具来研究IM30蛋白保护细胞膜的机制。我们的团队由来自英国5所不同大学的微生物学家、生物物理学家、生物化学家、遗传学家和细胞生物学家组成，他们将共同改变对IM30蛋白质功能的理解，以及更广泛地说，细胞如何保护自己免受环境侮辱。

All living cells are surrounded by a thin membrane, which keeps the inside of the cell separate from the outside environment. This essential cellular boundary layer contains proteins that allow the cell to take up food and expel waste products. The membrane is also energised, which means that cells actively generate and maintain ion gradients and voltage across the membrane. This so-called electrochemical gradient is one of the key cellular methods to store energy, and which can be utilised to drive uptake of nutrients and expel waste products. Furthermore, electrochemical gradient is critical for the synthesis of ATP, which is a key molecule used to energise intracellular processes. Hence, the integrity of the membrane is central to the proper function of living cells, and many known toxins including some antibiotics act by disrupting the membrane. During the early evolution of cells, a protein named IM30 evolved that has a role in protecting the membrane in the presence of damaging agents. These proteins, discovered just over 30 year ago, have been found to adopt ring-like structures that can stack upon each other to form tubes. Further, these proteins are known to accumulate in cells to very high levels when their membrane is damaged, and directly bind to cell membranes. However, how they protect the membrane, allowing the electrochemical potential to be maintained, is unknown. In this project we have assembled a diverse team of researchers at different stages in their career and with different sets of expertise. We all share the interest in trying to figure out how the IM30 proteins work to protect cellular membranes. They could potentially do this by forming a coat covering the inside of the membrane, by forming 'ribs' that wrap around the cell and hold the membrane together, or by allowing the membranes to form small fragments that carry away the toxin that is damaging the cell. Alternatively, they might specifically project the proteins that generate the electrochemical potential or use it make ATP. Currently, we simply do not know. Whatever the mechanism is, however, it will be a completely new one and tell us important fundamental information about how biological membranes are organised and function. To figure out how these proteins function, we will use a large number of different microbial species, as these represent relatively simple cells that we can study effectively, and where we know IM30s are important. We will systematically characterise how much of the protein different cells contain, where in the cells the proteins a localised, whether they assemble into rings and rods inside the cell, and how their function is regulated by other factors. We will develop new techniques to measure the electrochemical gradient in real time in living cells, which will provide us with essential tools to study the mechanisms through which IM30 proteins protect cell membranes. Our team comprises of microbiologists, biophysicist, biochemists, geneticists and cell biologists at 5 different Universities in the UK, who will come together to bring about a step change in understanding of IM30 protein function, and more generally how cells protect themselves from environmental insult.