REGULATION OF GLUTAMINE SYNTHETASE IN STREPTOMYCES

链霉菌属物种合成70多种医学上重要的 抗生素以及抗肿瘤和抗寄生虫剂。 这些化合物 在营养限制期间作为次级代谢产物产生， 孢子形成的开始。 然而，监管的机制 链霉菌中次级代谢和孢子形成起始不 明白 谷氨酰胺合成酶（GS）是合成 在氮同化中，抗生素放线菌红素增加， 在S.天蓝色。 的调查 GS在其他细菌系统中的调节已经确定了全球性的 响应氮激活基因表达的调控网络 空房的 GS基因将被用作研究调控的手柄。 氮素营养过程中基因表达改变的机制 链霉菌的限制。 将采用两种方法来研究 GS基因在S.天蓝色。 首先，S.天蓝色GS 本实验室克隆的结构基因（glnA）将被 物理表征以确定glnA启动子和编码区。 其次，将从遗传学角度确定参与GS调控的因素 通过分离合成GS能力改变的突变体。 的 glnA克隆的DNA将用于研究 glnA启动子和遗传鉴定的GS调节蛋白，RNA 聚合酶和小的含氮化合物。 了解 链霉菌GS的氮调节机制 允许使用合理的策略来增加产量， 抗生素和其他次级代谢产物，并分离新的 次级代谢产物 此外，应该有可能制定一个 更好地了解参与的监管机制， 链霉菌次级代谢和产孢起始。

Streptomyces species synthesize more than 70 medically important antibiotics as well as antitumor and antiparasitic agents. These compounds are produced as secondary metabolites during nutritional limitation and the initiation of sporulation. However, the mechanisms which regulate the initiation of secondary metabolism and sporulation in Streptomyces are not understood. The synthesis of both glutamine synthetase (GS), a key enzyme in nitrogen assimilation, and the antibiotic, actinorhodin, are increased during nitrogen limitation in S. coelicolor. Investigations of the regulation of GS in other bacterial systems have identified global regulatory networks which activate gene expression in response to nitrogen availability. The GS gene will be used as a handle for studying regulatory mechanisms responsible for alterations in gene expression during nitrogen limitation in Streptomyces. Two approaches will be used to investigate the regulation of the GS gene in S. coelicolor. First, the S. coelicolor GS structural gene (glnA) which has been cloned in this laboratory will be physically characterized to determine the glnA promoter and coding region. Secondly, factors involved in GS regulation will be identified genetically by the isolation of mutants altered in the ability to synthesize GS. The glnA cloned DNA will then be used to study the interactions between the glnA promoter and the genetically identified GS regulatory proteins, RNA polymerase and small nitrogen-containing compounds. An understanding of the mechanisms which mediate nitrogen regulation of GS in Streptomyces will allow rational strategies to be used for the increased production of antibiotics and other secondary metabolites, and the isolation of novel secondary metabolites. Furthermore, it should be possible to develop a better understanding of the regulatory mechanisms involved in the initiation of secondary metabolism and sporulation in Streptomyces.