Departamento de Bioquímica e Biologia Molecular, UFPR, Curitiba, PR, Brazil.
Departamento de Bioquímica e Biologia Molecular, UFPR, Curitiba, PR, Brazil; Departamento de Análises Clínicas, UFPR, Curitiba, PR, Brazil.
J Proteomics. 2018 Mar 1;174:28-35. doi: 10.1016/j.jprot.2017.12.006. Epub 2017 Dec 21.
The carbohydrate-uptake phosphorelay PTS system plays a key role in metabolic regulation in Bacteria controlling the utilization of secondary carbon sources. Some bacteria, such as Escherichia coli, encode a paralogous system named PTS (nitrogen related PTS). PTS is composed of EI (ptsP), NPr (ptsO), and EIIA (ptsN). These proteins act as a phosphorelay system from phosphoenolpyruvate to EI, NPr and them to EIIA. PTS is not involved in carbohydrate uptake and it may be dedicated to performing regulatory functions. The phosphorylation state of EI is regulated by allosteric binding of glutamine and 2-oxoglutarate, metabolites whose intracellular levels reflect the nitrogen status. Although PTS is designated as having nitrogen-sensory properties, no major effect of this system on nitrogen regulation has been described in E. coli. Here we show that an E. coli ptsN deletion mutant has impaired growth in minimal medium. Proteome analysis of the ∆ptsN strain under different nitrogen regimes revealed no involvement in regulation of the canonical nitrogen regulatory (Ntr) system. The proteomic data support the conclusion that ptsN is required to balance the activities of the sigma factors RpoS and RpoD in such way that, in the absence of ptsN, RpoS-dependent genes are preferentially expressed.
The nitrogen related PTS phosphorelay system has been hypothesized to participate in the control of nitrogen metabolism. Here we used a proteomics approach to show that an Escherichia coli ptsN null strain, which misses the final module of PTS phosphorelay, has no significant effects on nitrogen metabolism under different nitrogen regimes. We noted that ptsN is required for fitness under minimal medium and for the proper balance between RpoS and sigma 70 activities in such way that, in the absence of ptsN, RpoS-dependent genes are preferentially expressed.
碳水化合物摄取磷酸接力 PTS 系统在代谢调节中起着关键作用，控制着细菌对次生碳源的利用。一些细菌，如大肠杆菌，编码了一个名为 PTS（氮相关 PTS）的旁系同源系统。PTS 由 EI（ptsP）、NPr（ptsO）和 EIIA（ptsN）组成。这些蛋白质作为磷酸接力系统，从磷酸烯醇丙酮酸到 EI、NPr，再到 EIIA。PTS 不参与碳水化合物摄取，它可能专门用于执行调节功能。EI 的磷酸化状态受谷氨酰胺和 2-氧戊二酸的变构结合调节，这些代谢物的细胞内水平反映了氮的状态。尽管 PTS 被指定为具有氮感应特性，但在大肠杆菌中尚未描述该系统对氮调节的主要影响。在这里，我们表明大肠杆菌 ptsN 缺失突变体在最小培养基中的生长受到损害。在不同氮条件下对 ∆ptsN 菌株的蛋白质组分析显示，该系统与典型的氮调节（Ntr）系统的调节无关。蛋白质组数据支持 ptsN 被需要平衡 sigma 因子 RpoS 和 RpoD 的活性的结论，以至于在没有 ptsN 的情况下，RpoS 依赖的基因优先表达。
氮相关 PTS 磷酸接力系统被假设参与氮代谢的控制。在这里，我们使用蛋白质组学方法表明，大肠杆菌 ptsN 缺失突变体缺失 PTS 磷酸接力的最后一个模块，在不同氮条件下对氮代谢没有显著影响。我们注意到 ptsN 是在最小培养基中适应和在 RpoS 和 sigma 70 活性之间适当平衡所必需的，以至于在没有 ptsN 的情况下，RpoS 依赖的基因优先表达。
