Processing of cell surface lipoproteins in Streptomyces coelicolor. A new paradigm?

天蓝色链霉菌细胞表面脂蛋白的加工。

基本信息

批准号：
BB/F009429/1
负责人：
Matthew Hutchings
金额：
$ 40.07万
依托单位：
University of East Anglia
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2007
资助国家：
英国
起止时间：
2007 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=BB%2FF009429%2F1
关键词：
Processing cell surface lipoproteins Streptomyces

项目摘要

Bacteria can be divided into two main groups; Gram negative bacteria have two membranes surrounding the cell, the cytoplasmic membrane and the outer membrane. They also have a space between these membranes called the periplasm. Proteins which are exported across the cytoplasmic membrane typically end up in the periplasm. Gram positive bacteria have only a single membrane, surrounded by a thick cell wall. Proteins which are exported across the membrane must be anchored to the outer surface of the membrane, or the cell wall, to avoid being lost entirely from the cell. These cell surface proteins act as a point of contact with the outside world and are involved in a number of essential processes including sensing environmental changes, protein folding, respiration and nutrient scavenging. They also have an important role in surface attachment and are essential for successful host infection in disease-causing bacteria. One of the main ways in which bacteria attach proteins to their membranes is by attaching a lipid molecule to the N-terminal end of the protein. The widely accepted model suggests that these 'lipoproteins' are first targeted to the Sec (secretion) pathway by a signal sequence at the N-terminus of the protein. Sec transports them across the cytoplasmic membrane to the outside of the cell where an enzyme called Lgt attaches the lipid molecule. The signal sequence is then cleaved by an enzyme called Lsp. In Gram positive bacteria the pathway ends here and the proteins are attached to the outer face of the membrane. In Gram negative bacteria these proteins have another lipid molecule attached by an enzyme called Lnt and this allows them to be transported to the outer membrane. Only a small proportion is retained in the inner membrane. In Gram negative bacteria all the enzymes involved in lipoprotein biosynthesis are essential, probably because removing any one of them results in lipoproteins accumulating in, and destabilising, the inner membrane. In Gram positive bacteria they are essential for the virulence of many disease-causing organisms. They therefore represent an excellent target for new antibacterial drugs such as globomycin, a strong inhibitor of Lsp. We have been studying lipoprotein biosynthesis in the Gram positive bacterium Streptomyces coelicolor, and have discovered some surprising differences which could challenge the widely accepted model. Previously it was assumed that all lipoproteins were exported by Sec but this is not the case in S. coelicolor. We have good evidence that some S. coelicolor lipoproteins can be exported by the Tat secretion pathway. While Sec transports linear proteins, Tat is typically used to transport fully folded proteins which are assembled inside the cell. This challenges the current model and it also suggests that the Lgt enzyme can attach lipids to both linear and fully folded proteins. S. coelicolor is unusual in that it contains two Lgt enzymes and it is possible that one acts on Sec-, and the other on Tat-dependent lipoproteins. Finally, and perhaps most puzzlingly of all, S. coelicolor contains two Lnt enzymes. This enzyme performs a step previously thought to be unique to Gram negative bacteria. Since Gram positive bacteria do not have an outer membrane the function of these enzymes in S. coelicolor are unclear. In this study we will investigate the differences in the export and modification of Tat- and Sec-dependent lipoproteins. We will examine the functions of the two Lgt enzymes in these processing pathways. We will also test the activities of the Lnt enzymes to see if they have the same function as Lnt in Gram negative bacteria. We anticipate that the results of this study will lead to a paradigm shift in our understanding of bacterial lipoprotein biosynthesis.

细菌可分为两大类：革兰氏阴性细菌的细胞周围有两层膜，即细胞质膜和外膜。它们的膜之间还有一个称为周质的空间。穿过细胞质膜输出的蛋白质通常最终进入周质。革兰氏阳性细菌只有一层膜，周围有厚厚的细胞壁。跨膜输出的蛋白质必须锚定在膜的外表面或细胞壁上，以避免从细胞中完全丢失。这些细胞表面蛋白充当与外界的接触点，并参与许多重要过程，包括感知环境变化、蛋白质折叠、呼吸和营养物清除。它们在表面附着方面也具有重要作用，并且对于成功感染致病细菌的宿主至关重要。细菌将蛋白质附着在其膜上的主要方式之一是将脂质分子附着在蛋白质的 N 末端。广泛接受的模型表明，这些“脂蛋白”首先通过蛋白质 N 末端的信号序列靶向 Sec（分泌）途径。 Sec 将它们穿过细胞质膜运输到细胞外部，在那里一种名为 Lgt 的酶附着脂质分子。然后信号序列被称为 Lsp 的酶切割。在革兰氏阳性细菌中，该途径在此结束，蛋白质附着在膜的外表面。在革兰氏阴性细菌中，这些蛋白质具有另一种由 Lnt 酶附着的脂质分子，这使得它们能够被转运到外膜。仅一小部分保留在内膜中。在革兰氏阴性细菌中，参与脂蛋白生物合成的所有酶都是必需的，可能是因为去除其中任何一种酶都会导致脂蛋白在内膜中积累并不稳定。在革兰氏阳性细菌中，它们对于许多致病生物体的毒力至关重要。因此，它们代表了新型抗菌药物（如球霉素（Lsp 的强抑制剂））的绝佳靶标。我们一直在研究革兰氏阳性细菌天蓝色链霉菌的脂蛋白生物合成，并发现了一些令人惊讶的差异，这些差异可能会挑战广泛接受的模型。以前假设所有脂蛋白都是由 Sec 输出的，但天蓝色链球菌的情况并非如此。我们有充分的证据表明一些天蓝色链球菌脂蛋白可以通过 Tat 分泌途径输出。 Sec 运输线性蛋白质，而 Tat 通常用于运输在细胞内组装的完全折叠的蛋白质。这挑战了当前的模型，并且还表明 Lgt 酶可以将脂质附着到线性和完全折叠的蛋白质上。天蓝色链球菌的不同寻常之处在于它含有两种 Lgt 酶，其中一种可能作用于 Sec-，另一种则作用于 Tat 依赖性脂蛋白。最后，也许最令人困惑的是，天蓝色链球菌含有两种 Lnt 酶。这种酶执行以前被认为是革兰氏阴性细菌独有的步骤。由于革兰氏阳性菌没有外膜，因此这些酶在天蓝色链球菌中的功能尚不清楚。在这项研究中，我们将研究 Tat 和 Sec 依赖性脂蛋白的输出和修饰的差异。我们将研究两种 Lgt 酶在这些加工途径中的功能。我们还将测试Lnt酶的活性，看看它们是否与革兰氏阴性菌中的Lnt具有相同的功能。我们预计这项研究的结果将导致我们对细菌脂蛋白生物合成的理解发生范式转变。

项目成果

期刊论文数量（10）

专著数量（0）

科研奖励数量（0）

会议论文数量（0）

专利数量（0）

Mammalian cell entry genes in Streptomyces may provide clues to the evolution of bacterial virulence.

DOI：
10.1038/srep01109
发表时间：
2013
期刊：
SCIENTIFIC REPORTS
影响因子：
4.6
作者：
Clark, Laura C.;Seipke, Ryan F.;Prieto, Pilar;Willemse, Joost;van Wezel, Gilles P.;Hutchings, Matthew I.;Hoskisson, Paul A.
通讯作者：
Hoskisson, Paul A.

Cosmid based mutagenesis causes genetic instability in Streptomyces coelicolor, as shown by targeting of the lipoprotein signal peptidase gene.

DOI：
10.1038/srep29495
发表时间：
2016-07-12
期刊：
Scientific reports
影响因子：
4.6
作者：
Munnoch JT;Widdick DA;Chandra G;Sutcliffe IC;Palmer T;Hutchings MI
通讯作者：
Hutchings MI

The transcriptional repressor protein NsrR senses nitric oxide directly via a [2Fe-2S] cluster.

DOI：
10.1371/journal.pone.0003623
发表时间：
2008
期刊：
PloS one
影响因子：
3.7
作者：
Tucker NP;Hicks MG;Clarke TA;Crack JC;Chandra G;Le Brun NE;Dixon R;Hutchings MI
通讯作者：
Hutchings MI

Cosmid based mutagenesis causes genetic instability in Streptomyces coelicolor , as shown by targeting of the lipoprotein signal peptidase gene

基于粘粒的诱变导致天蓝色链霉菌遗传不稳定，如脂蛋白信号肽酶基因靶向所示。