REGULATION OF HISTIDINE UTILIZATION IN STREPTOMYCES

链霉菌对氨基酸L-组氨酸的利用， 控制在基因表达和酶活性的水平。 组氨酸氨裂解酶（组氨酸酶），催化第一个 组氨酸转化为谷氨酸的一步，是在 在灰色链霉菌中，通过至少以下物质的协同作用， 三种蛋白质 这些蛋白质中的一种可以在体外被一种 在一些实施方案中，一种酶可以被磷酸二酯酶替代，另一种可以被磷酸二酯酶替代。 的 建议的实验已经被设计来识别和表征 参与控制组氨酸酶活性的基因和基因产物， S.灰色的 不能激活组氨酸酶的突变体的分析将 有助于阐明组氨酸酶被激活的机制 in vivo. 组氨酸酶的无活性和活性形式将通过以下方法鉴定： 电泳和免疫学技术的结合。 到 确定组氨酸酶活性是否响应于 链霉菌的生命周期， 将测量分化期间的这些形式。 活化因子， 将组氨酸酶转化为催化活性形式的蛋白质将 纯化、活性鉴定和结构基因克隆。 组氨酸酶结构基因也将被克隆，以便于分析 组氨酸酶活性的调节，并允许鉴定 组氨酸酶基因表达的分子特征。 通过这些研究， 更详细地了解参与调节的分子 链霉菌的氮代谢。 这项研究也可能 延伸到监管过程的分支， 细胞分化和次级代谢。

The utilization of the amino acid L-histidine by streptomycetes is controlled at the levels of gene expression and enzymatic activity. Histidine ammonia-lyase (histidase), the enzyme that catalyzes the first step in the conversion of histidine to glutamate, is regulated post- translationally in Streptomyces griseus by the concerted action of at least three proteins. One of these proteins can be replaced in vitro by a phosphatase, and another can be replaced by a phosphodiesterase. The proposed experiments have been designed to identify and characterize the genes and gene products involved in the control of histidase activity in S. griseus. The analysis of mutants that cannot activate histidase will facilitate the elucidation of the mechanism by which histidase is activated in vivo. The inactive and active forms of histidase will be identified by a combination of electrophoretic and immunological techniques. To determine whether histidase activity is regulated in response to changes in the streptomycete life cycle, fluctuatuations in the relative amounts of these forms during differentiation will be measured. Activation factor, the protein that converts histidase to the catalytically active form, will be purified, its activity characterized, and its structural gene cloned. The histidase structural gene will also be cloned, to facilitate analysis of the regulation of histidase activity and to permit the identification of molecular features of histidase gene expression. By these studies, we will gain a more detailed understanding of molecules involved in the regulation of nitrogen metabolism in streptomycetes. This research may also have ramifications extending to a regulatory processes functional during cellular differentiation and secondary metabolism.