Microbial Diversity in Mechanisms of Disulfide Bond Formation and Reduction

描述（由申请人提供）：我们将确定在某些细菌和古细菌中发现的两种新型蛋白质二硫键形成途径的性质。E.大肠杆菌和许多其他细菌使用两种酶将二硫键引入蛋白质。DsbA直接将蛋白质的半胱氨酸连接成二硫键，而DsbB再氧化并因此再生活性DsbA。许多其他细菌，包括结核分枝杆菌（Mtb），似乎使用人类维生素K环氧化物还原酶VKOR的同系物来形成二硫键，而不是DsbB。Mtb VKOR可以替代E.杆菌我们将通过定义哪些基因产物包含这种氧化途径，在大肠杆菌和大肠杆菌中表达候选基因，来表征分枝杆菌基于VKOR的二硫键形成系统。大肠杆菌和耻垢分枝杆菌（比Mtb更易处理）。在某些古细菌中，我们已经获得了另一种不寻常的细胞质中二硫键形成途径的证据。这些古细菌含有两个VKORs，一个面向细胞质，显然参与细胞质二硫键的形成。我们将验证这一途径，并确定细胞质基板（细胞质“DsbA”？）这VKOR氧化。我们将通过在大肠杆菌中表达和操纵候选基因来测试该VKOR的拟议作用。大肠杆菌和古菌硫磺硫化叶菌。我们实验室开发的用于分析细胞质和周质中二硫键形成的一系列测定和遗传技术将极大地促进这些研究和其他实验室进行的研究。 在我们的实验室里，我们已经进化出了E.大肠杆菌中使用新的途径形成或还原二硫键。我们假设有其他的原核生物，使用这些相同的电子传递途径自然。我们将测试这一假设如下：我们将使用生物信息学分析，我们已经开发来评估其他生物体的能力，使二硫键。然后，我们将使用已测序的细菌基因组的生物信息学分析来鉴定可能缺乏E途径基因的原核生物。大肠杆菌用于这些目的，但包含的基因，其产物可能构成一个新的途径。然后我们将研究这些来自其他生物的候选基因在大肠杆菌中表达时的特性。大肠杆菌和原生生物本身。 我们将使用化学生物学方法研究DsbB和VKOR功能，以获得DsbB和VKOR抑制剂的小分子。我们将使用一种高灵敏度的二硫键形成测定法，筛选大量抑制大肠杆菌的化学物质。coli DsbB和Mtb VKOR。这些化学物质将被用来剖析这两种蛋白质的作用步骤，通过抗性突变来确定作用位点，并对VKORs和DsbB进行比较研究。还将筛选抑制剂的活性，作为开发抗结核病的潜在抗生素和抗凝血剂的候选物。（人VKOR是凝血途径的一个组成部分。

DESCRIPTION (provided by applicant): We will establish the nature of two novel protein disulfide bond-forming pathways found in certain bacteria and archaea. E. coli and many other bacteria use two enzymes to introduce disulfide bonds into proteins. DsbA directly joins the cysteines of proteins into disulfide bonds while DsbB reoxidizes and thus regenerates active DsbA. Many other bacteria, including Mycobacterium tuberculosis (Mtb), appear to use a homologue of human vitamin K epoxide reductase, VKOR, for disulfide bond formation instead of DsbB. Mtb VKOR can substitute for DsbB in E. coli. We will characterize the mycobacterial VKOR-based disulfide-bond forming system by defining which gene products comprise this oxidative pathway, expressing candidate genes in both E. coli and Mycobacterium smegmatis (which is more tractable than Mtb). In certain archaea, we have obtained evidence for another unusual pathway for disulfide bond formation in the cytoplasm. These archaea contain two VKORs, one cytoplasmically-oriented and apparently involved in cytoplasmic disulfide bond formation. We will verify this pathway and identify the cytoplasmic substrate (a cytoplasmic "DsbA"?) that this VKOR oxidizes. We will test the proposed role of this VKOR by expressing and manipulating candidate genes both in E. coli and the archaeon Sulfolobus solfataricus. The array of assays and genetic techniques developed in our lab for analyzing disulfide bond formation in the cytoplasm and periplasm will greatly facilitate these studies and those carried out in other laboratories. In our laboratory, we have evolved strains of E. coli that use novel pathways for disulfide bond formation or reduction. We hypothesize that there are other prokaryotes that use these same electron transfer pathways naturally. We will test this hypothesis as follows: we will use bioinformatic analyses that we have developed to assess the capacity of other organisms to make disulfide bonds. We will then use bioinformatic anlaysis of bacterial genomes that have been sequenced to identify prokaryotes that may lack the genes for the pathways E. coli uses for these purposes, but contain genes whose products might constitute one of the novel pathways. We will then study the properties of these candidate genes from other organisms when they are expressed in E. coli and within the native organism itself. We will study DsbB and VKOR function using a chemical biology approach to obtain small molecules that are inhibitors of DsbB and VKOR. Using a highly sensitive assay for disulfide bond formation, we will screen a large library of chemicals for inhibition of E. coli DsbB and Mtb VKOR. These chemicals will be used to dissect out the steps in the action of these two proteins, to define sites of action through resistant-mutations, and to do comparative studies of VKORs and DsbB. The inhibitors will also be screened for their activity as candidates for development as potential antibiotics against tuberculosis and as anti-coagulants. (Human VKOR is a component of the blood coagulation pathway.)