Structure and function of steptomyces RNA polymerase

该菌具有独特的生活史，在形态和生理上具有复杂的分化。在固体培养基上，该菌作为基质菌丝体生长，延伸形成气生菌丝并最终分化为外孢子。在孢子形成的某些阶段，它们产生多种抗生素。从大肠杆菌基因表达调控的知识来看，RNA聚合酶的启动子选择性的调节必然涉及链霉菌中基因转录的这种开关控制。为了测试这种可能性，首次从灰色链霉菌（S.greseus）中分离纯化了RNA聚合酶，并对其结构和功能进行了分析，发现该酶在生长期菌丝体中含有一个主要的sigma因子，由hrdB基因编码，并转录一些细胞生长所必需的基因，因此，我们的结论是Esigma-B（或E-HrdB）是指数生长细胞中主要的RNA聚合酶全酶。在分析RNA聚合酶的同时，正在收集S.griceus启动子，用于将来分析次要的sigma因子。

Steptomyces has a unique life cycle with a complex differentiation in morphology and physiology.On solid media, the bacteria grow as substrate mycelia which extend to form aerial hyphae and ulitimately differentiate into exospores.At certain plases during the sporulation, they produce varieties of antibiotics.From the knowledge of gene expression control in E.coli, the modulation of promoter selectivity of RNA polymerase must be involved in this switching control of gene transcription in Streptomyces.In order to test this possibility, RNA polymerase was purified for the first time from S.greseus and analyzed for its structure and function.The enzyme from vegetative-phase mycelia was found to contain a principal sigma factor encoded by the gene hrdB and to transcribe some essential genes for cell growth.Thus, we concluded that Esigma-B (or E-HrdB) is the major RNA polymerase holoenzyme in the exponentially growing cells.In parallel with the analysis of RNA polymerase, a collection of S.griceus promoters is being made for future analysis of minor sigma factors.