Rollenhagen Claudia, Antelmann Haike, Kirstein Janine, Delumeau Olivier, Hecker Michael, Yudkin Michael D
Institut für Mikrobiologie, Ernst-Moritz-Arndt-Universität, 17487 Greifswald, Germany.
J Bacteriol. 2003 Jan;185(1):35-40. doi: 10.1128/JB.185.1.35-40.2003.
In Bacillus subtilis, the alternative sigma factor sigma(B) is activated in response to environmental stress or energy depletion. The general stress regulon under the control of sigma(B) provides the cell with multiple stress resistance. Experiments were designed to determine how activated sigma(B) replaces sigma(A) as a constituent of the RNA polymerase holoenzyme. Studies of the transcription of the sigma(A)-dependent stress gene clpE under sigma(B)-inducing conditions showed that expression was higher in a sigB mutant background than in the wild type. The relative affinities of sigma(A) and sigma(B) for binding to the core RNA polymerase (E) were determined by means of indirect surface plasmon resonance. The results showed that the affinity of sigma(B) for E was 60-fold lower than that of sigma(A). Western blot analyses with antibodies against sigma(A), sigma(B), and E showed that, after exposure to ethanol stress, the concentration of sigma(B) was only twofold higher than those of sigma(A) and E. Thus, the concentration of sigma(B) after stress is not high enough to compensate for its relatively low affinity for E, and it seems that additional mechanisms must be invoked to account for the binding of sigma(B) to E after stress.
在枯草芽孢杆菌中，替代σ因子σ（B）会响应环境压力或能量耗竭而被激活。在σ（B）控制下的一般应激调节子为细胞提供多种应激抗性。设计实验以确定激活的σ（B）如何取代σ（A）作为RNA聚合酶全酶的组成部分。在σ（B）诱导条件下对依赖σ（A）的应激基因clpE转录的研究表明，在sigB突变体背景下的表达高于野生型。通过间接表面等离子体共振测定σ（A）和σ（B）与核心RNA聚合酶（E）结合的相对亲和力。结果表明，σ（B）与E的亲和力比σ（A）低60倍。用抗σ（A）、σ（B）和E的抗体进行的蛋白质免疫印迹分析表明，在暴露于乙醇应激后，σ（B）的浓度仅比σ（A）和E高两倍。因此，应激后σ（B）的浓度不足以弥补其对E相对较低的亲和力，似乎必须调用其他机制来解释应激后σ（B）与E的结合。
