Carbon Catabolite Repression in Bacillus subtilis: Quantitative Analysis of Repression Exerted by Different Carbon Sources
Carbon Catabolite Repression in Bacillus subtilis: Quantitative Analysis of Repression Exerted by Different Carbon Sources
复制标题
DOI：
10.1128/jb.00848-08
复制
发表时间：
2008-11-01
影响因子：
3.2
通讯作者：
Goerke, Boris
中科院分区：
文献类型：
--
作者：
Singh, Kalpana D.;Schmalisch, Matthias H.;Goerke, Boris
在许多细菌中，葡萄糖是首选的碳源，抑制次级底物的利用。在枯草芽孢杆菌中，这种碳分解代谢抑制（CCR）是由全局转录调节剂CcpA实现的，其活性是由其磷酸化的辅助因子HPr（Ser46-P）和Crh（Ser46-P）的可用性触发的。这些蛋白的磷酸化是由代谢产物控制的激酶HPrK/P催化的。最近的研究集中在葡萄糖作为一种抑制底物。这里，我们展示了许多碳水化合物引起CCR。通过ccpa介导的CCR通路，底物在其施加抑制的能力上形成了一个等级。在这两种辅助因子中，HPr足以实现完全的CCR。相比之下，Crh不能代替HPr在底物上引起强烈的抑制。体内HPr磷酸化状态的测定揭示了抑制强度与HPr Ser46位点磷酸化程度之间的相关性。由磷酸转移酶系统（PTS）运输的糖引起最强的抑制。然而，HPr在其His15残基的磷酸化状态和PTS转运活性对全局CCR机制没有影响，这与大肠杆菌中的机制存在主要差异。我们的数据表明，不同底物在CCR中的等级完全取决于HPrK/P的活性。
In many bacteria glucose is the preferred carbon source and represses the utilization of secondary substrates. In Bacillus subtilis, this carbon catabolite repression (CCR) is achieved by the global transcription regulator CcpA, whose activity is triggered by the availability of its phosphorylated cofactors, HPr(Ser46-P) and Crh(Ser46-P). Phosphorylation of these proteins is catalyzed by the metabolite- controlled kinase HPrK/P. Recent studies have focused on glucose as a repressing substrate. Here, we show that many carbohydrates cause CCR. The substrates form a hierarchy in their ability to exert repression via the CcpA-mediated CCR pathway. Of the two cofactors, HPr is sufficient for complete CCR. In contrast, Crh cannot substitute for HPr on substrates that cause a strong repression. Determination of the phosphorylation state of HPr in vivo revealed a correlation between the strength of repression and the degree of phosphorylation of HPr at Ser46. Sugars transported by the phosphotransferase system (PTS) cause the strongest repression. However, the phosphorylation state of HPr at its His15 residue and PTS transport activity have no impact on the global CCR mechanism, which is a major difference compared to the mechanism operative in Escherichia coli. Our data suggest that the hierarchy in CCR exerted by the different substrates is exclusively determined by the activity of HPrK/P.