ABSTRACT
The nitrogen phosphotransferase system (PTS(Ntr)) of Pseudomonas putida is a key regulatory device that participates in controlling many physiological processes in a posttranscriptional fashion. One of the target functions of the PTS(Ntr) is the regulation of potassium transport. This is mediated by the direct interaction of one of its components with the sensor kinase KdpD of the two-component system controlling transcription of the kdpFABC genes. From a detailed experimental analysis of the activity of the kdpF promoter in P. putida wild-type and pts mutant strains with varying potassium concentrations, we had highly time-resolved data at hand, describing the influence of the PTS(Ntr) on the transcription of the KdpFABC potassium transporter. Here, this data was used to construct a mathematical model based on a black box approach. The model was able to describe the data quantitatively with convincing accuracy. The qualitative interpretation of the model allowed the prediction of two general points describing the interplay between the PTS(Ntr) and the KdpFABC potassium transporter: (1) the influence of cell number on the performance of the kdpF promoter is mainly by dilution by growth and (2) potassium uptake is regulated not only by the activity of the KdpD/KdpE two-component system (in turn influenced by PtsN). An additional controller with integrative behavior is predicted by the model structure. This suggests the presence of a novel physiological mechanism during regulation of potassium uptake with the KdpFABC transporter and may serve as a starting point for further investigations.
Subject(s)
Cation Transport Proteins/genetics , Cation Transport Proteins/metabolism , Gene Expression Regulation, Bacterial , Phosphoenolpyruvate Sugar Phosphotransferase System/genetics , Phosphoenolpyruvate Sugar Phosphotransferase System/metabolism , Potassium/metabolism , Pseudomonas putida/metabolism , Bacterial Proteins/genetics , Bacterial Proteins/metabolism , Escherichia coli/genetics , Models, Biological , Mutation , Phosphorylation , Promoter Regions, Genetic , Protein Binding , Protein Kinases/genetics , Protein Kinases/metabolism , Pseudomonas putida/genetics , Pseudomonas putida/growth & developmentABSTRACT
The nitrogen phosphotransferase system (PTS(Ntr) ) of Pseudomonas putida is a multi-component regulatory device that participates in controlling a variety of physiological processes in a post-translational fashion. A general survey of genes regulated by PtsN exposed transcription of the kdpFABC operon is most conspicuously affected. Measurements of kdpFp promoter activity in different pts mutants showed that PtsN is responsible for repression of kdpFABC transcription. This effect could be assigned mainly to PtsNâ¼P, depending on the external K(+) concentration. Bacterial two-hybrid assays demonstrated that kdpFp regulation is implemented through direct interaction of the PtsN protein with the sensor kinase KdpD of the KdpD/KdpE two-component system. Interaction between KdpD and PtsN was detectable with a PtsN variant that imitates the non-phosphorylated form as well as with a PtsN type mimicking the phosphorylated form of PtsN. These results raise a regulatory scenario in which the Kdp system is regulated by the action of PtsN through direct interaction with the sensor kinase KdpD, and the outcome of such an interaction depends on the phosphorylation state of PtsN as well as on the external K(+) concentration.
