Discovery of a cryptic sphingolipid pathway in E.coli - structural and functional analysis.

一个非常重要的生物分子大家族被称为脂类。它们包括脂肪和类固醇，如胆固醇。另一个重要的亚家族是神经鞘脂(SLS)和神经酰胺(就像有两条尾巴的SLS)。所有这些脂质都存在于细胞膜中--科学家发现，动物、植物和细菌细胞都有一个具有保护性的防水外壳，外壳由具有亲水(亲水)头部基团和长长的憎水(疏水)尾巴的分子组成。正是这些分子提供了这一层。然而，它们不仅仅是结构上的作用--它们已经被证明在细胞分裂和细胞之间交流时起着重要作用。每个细胞中的脂质都有很高的周转率，它们不断地被制造和分解。这是受到严格控制的。特别是，SL水平的变化与老年和阿尔茨海默氏症、帕金森氏病、糖尿病、哮喘、癌症和神经消耗疾病等疾病密切相关。很少能找到同时由植物、动物和细菌组成的分子；SLS和神经酰胺正是如此--它们是由100个分子组成的非常大的家族，每个分子略有不同--它们含有氨基酸、脂肪酸和糖。然而，核心结构是相同的。对人类健康有直接影响的一个令人兴奋的研究领域是发现人类是许多不同类型细菌的宿主--这些细菌统称为微生物群/微生物群。这些细菌生活在我们的口腔、皮肤和肠道中，帮助我们代谢食物，也被认为起到了保护作用。它们让我们保持健康；所以我们必须了解细菌什么时候是好的，什么时候是有害的？化学诱因是什么？每个细胞通过使用简单的积木通过一个多步骤的途径来制造SLS--这些步骤由称为酶的分子机器催化(加速)。近年来，研究集中在参与人类SL生物合成的酶上，但对微生物如何合成这些酶知之甚少。当我们与美国科学家合作发现，生活在淡水中的一种简单、安全的Caulbacter细菌可以产生与我们相同的核心SLS时，我们取得了突破，但它使它们通过一条不同的路线--这称为聚合进化。然后，我们使用遗传学来研究其他细菌的DNA--我们认为存在于少数微生物中的DNA更广泛。我们甚至在大肠杆菌中发现了它们--一种非常常见的细菌，可以是好的，也可以是坏的。科学家使用大肠杆菌已经有很多年了，因为它们是安全的，易于种植，易于工程设计，我们对它们的工作原理有一个蓝图。现在我们有了一个令人兴奋的发现，即大肠杆菌产生SLS，我们想要了解这个过程的分子细节-我们将研究涉及的酶。我们将确定关键的SPT酶的3D结构以及它如何与脂质载体结合。我们将探索SLS的两条脂链是如何安装的。我们还将在特殊标记的积木中培养大肠杆菌，这将揭示核心分子是如何构成的。这是英国和美国科学家各自将自己的专业知识带到这个项目中的团队努力。我们将使用我们作为化学家、微生物学家和分子生物学家的技能来揭开迄今隐藏在大肠杆菌中的秘密。我们的结果将引起学术微生物学家和化学家以及那些对分子如何进化感兴趣的人的兴趣。我们正在建立一个名为Lipid Maps的清单，其中包含了自然界中所有重要的脂质分子。因为50年来，大肠杆菌一直是一种模式微生物，所以很难找到新的东西--所以在这一领域工作是令人兴奋的。

A very important, large family of biological molecules are called lipids. They include fats and steroids such as cholesterol. Another important sub-family are known as sphingolipids (SLs) and ceramides (which are like SLs with two tails). All these lipids are found in the cell membrane - scientists have found that animal, plants and bacterial cells have a protective, water-resistant outer shell that is composed of molecules with a water-loving (hydrophilic) head group and a long, water-hating (hydrophobic) tail. It is these molecules that provide that layer. However, they don't just have a structural role - they have been shown to be important when cells divide and when cells communicate with each other. There is a high turnover of lipids in the every cell, they are constantly being made and broken down. This is tightly controlled. In particular, changes in SL levels are strongly linked with old age and diseases such as Alzheimer's, Parkinson's Disease, diabetes, asthma, cancer and nerve-wasting diseases. It is rare to find molecules made by both plants, animals and bacteria; SLs and ceramides are exactly that - they are very large family of 100s of molecules, each slightly different - they contain amino acids, fatty acids and sugars. However, the core structures are the same. An exciting area of research with direct implications for human health is the discovery that humans are hosts for many different types of bacteria - collectively these are known as the microbiota/microbiome. These bacteria live in our mouths, on our skin and in our gut and help us metabolise our food and are also thought to play protective roles. They keep us healthy; so we have to understand when is a bacteria good and when is a bacteria bad - pathogenic? What are the chemical triggers?Every cell make SLs by a multi-step pathway using simple building blocks - the steps are catalysed (sped up) by molecular machines called enzymes. In recent years, research has focussed on the enzymes involved in human SL biosynthesis but very little is known about how microbes make them. We made a breakthrough when we teamed up with American scientists to reveal that a simple, safe Caulobacter bacterium that lives in fresh water can make the same core SLs as we can, but it makes them through a different route - that's called convergent evolution. We then used genetics to look at the DNA of other bacteria - what we thought to present in a small number of microbes is more much more widespread. We have even found them in E. coli - a very common bacteria that can be good and bad. Scientists have used E. coli for many years because they are safe and easy to grow, easy to engineer and we have a blue-print of how they work. Now we have made an exciting discovery that E. coli make SLs we want to understand the molecular details of the process - we will study the enzymes involved. We will determine the 3D structure of the key SPT enzyme and how it engages with a lipid carrier. We will explore how the two lipids chains of SLs are installed. We will also grow E.coli in specially marked building blocks and that will reveal how the core molecules are made. This is a team effort with UK and USA scientists each bringing their own expertise to this project. We will use our skills as chemists, microbiologists and molecular biologists to uncover the secrets that have been hidden in E. coli until now. Our results will be of interest to academic microbiologists and chemists as well as those interested how molecules evolved. We are building a inventory called Lipid Maps of all the important lipid molecules in Nature. Because E. coli has been a model microbe for >50 years, it is rare to find something new - so it is exciting to work in this area.