Pahari S, Chatterji D
Centre for Cellular and Molecular Biology, Hyderabad, India.
FEBS Lett. 1997 Jul 7;411(1):60-2. doi: 10.1016/s0014-5793(97)00668-6.
Bacteriophage T4 produces a small protein AsiA, which inhibits transcription from sigma70-dependent promoters in E. coli by tightly binding to sigma70 and is therefore termed as anti-sigma factor. We observed that there was no inhibition of single round transcription at lac UV5 promoter when AsiA was added to preformed open complex between RNA polymerase and template DNA. However, transcription was found to proceed normally at 'extended -10' promoters in the presence of AsiA. It appears therefore that AsiA binds sigma70 at its 4.2-subdomain or in its close vicinity. Further experiments on immunoprecipitation of sigma70 and a mutant sigma70-V576G with AsiA seem to corroborate such conclusion.
噬菌体T4产生一种小蛋白AsiA，它通过与σ70紧密结合来抑制大肠杆菌中依赖σ70的启动子的转录，因此被称为抗σ因子。我们观察到，当将AsiA添加到RNA聚合酶与模板DNA之间预先形成的开放复合物中时，lac UV5启动子处的单轮转录没有受到抑制。然而，发现在存在AsiA的情况下，“延伸的-10”启动子处的转录正常进行。因此，似乎AsiA在其4.2亚结构域或其附近结合σ70。关于用AsiA对σ70和突变体σ70-V576G进行免疫沉淀的进一步实验似乎证实了这一结论。
