Study on signal transduction and involvement of protein synthesis machinery in the production of Bacilhus subtilis proteass

自然界中的微生物表现出各种不同的生活方式。枯草芽孢杆菌（Bacillus subtilis）是一种会遇到营养缺乏、干燥、剧烈温度变化等严重环境胁迫的土壤细菌。然而，细菌有各种方法来应对这些不利的情况。例如，在营养缺乏的情况下，它分泌蛋白酶和降解酶来消化碰巧存在于细胞周围的高分子量蛋白质或碳水化合物，并吸收水解产物作为营养。用于感知环境的机制被认为是一个双组分调节系统，在这个系统中，传感器激酶检测环境信号并磷酸化同源调节因子，然后激活目标基因。我们研究了一个涉及双组分系统的信号转导系统，DegS-DegU，它调节细胞外降解酶的产生。更一般地说，最有用的方法将是使用遗传手段。然而，对于DegS-DegU系统，许多遗传方法已经被应用，因此获得新发现的可能性似乎很低。因此，我们试图寻找可能影响DegS-DegU信号转导的化学制剂。结果发现，林可霉素和红霉素等已知通过影响核糖体功能抑制蛋白质生物合成的抗生素可以阻止碱性蛋白酶基因aprE的表达，aprE是DegS-DegU系统的靶标。在本研究中，我们试图确定DegS-DegU传递信号诱导aprE表达的抗生素靶点。我们发现林可霉素抑制rela依赖性ppGpp合成。此外，aprE的表达在rela缺陷细胞中显著降低。这些结果表明，林可霉素通过抑制ppGpp合成来抑制aprE的表达。这是首次报道抗生素抑制信号转导。我们还应用微阵列分析了枯草芽孢杆菌双组分系统，这些系统在调节因子中携带一个螺旋-转-螺旋基序，发现几个系统之间形成了网络。少

Microorganisms in nature show various modes of life style. Bacillus subtilis is a soil bacterium that encounters severe environmental stresses such as nutritional deficiency, desiccation, drastic temperature changes and so on. The bacterium, however, carries various means to cope with these unfavorable situations. Against nutritional deficiency, for example, it secretes proteases and degradative enzymes to digest high molecular weight proteins or carbohydrates that happen to be present around the cell, and takes up the hydrolyzed products for nutrition. The machinery that serves to sense the environment is thought to be the two-component regulatory system in which the sensor kinase detect environmental cues and phosphorylates the cognate regulator, which then activates the target genes.We have studied a signal transduction system involving a two-component system, DegS-DegU, which regulates the production of extracellular degradative enzymes. For the investigation of cellular processes … More in general, the most useful approach will be to use genetic means. For the DegS-DegU system, however, many genetic approaches have already been applied, and therefore the possibility to obtain new findings seemed to be low. We tried, therefore, to find chemical agents that might affect the signal transduction involving DegS-DegU. As a result, antibiotics such as lincomycin and erythromycin that are known to inhibit protein biosynthesis through affecting the ribosomal function were found to prevent the expression of the alkaline protease gene, aprE, the target of the DegS-DegU system. In this study we tried to identify the target of the antibiotics through which the DegS-DegU transmits a signal to induce the expression of aprE. We found that lincomycin inhibits RelA-dependent ppGpp synthesis. Furthermore, the expression of aprE was greatly reduced in relA-deficient cell. These results indicate that lincomycin prevents aprE expression by inhibiting ppGpp synthesis. This is the first report that an antibiotic inhibits signal transduction.We also applied microarray analysis on B. subtilis two-component systems that carry a helix-tum-helix motif in the regulator, and found that networks are formed among several of the systems. Less