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J. Bacteriol. doi:10.1128/JB.02002-07
Copyright (c) 2008, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.

Evidence of in vivo cross-talk between the nitrogen-related and fructose-related branches of the carbohydrate phosphotransferase system of Pseudomonas putida

Centro Nacional de Biotecnología-CSIC, Campus de Cantoblanco, Madrid 28049

^* To whom correspondence should be addressed. Email: vdlorenzo{at}cnb.csic.es.

	Abstract

The genome of Pseudomonas putida KT2440 encodes only 5 recognizable proteins belonging to the phosphoenlopyruvate-carbohydrate phosphotransferase system (PTS). Two of these PTS constituents (FruA and FruB) form a complete system for fructose intake. The other 3 products encoded by ptsP (EI^Ntr), ptsO (NPr) and ptsN (EIIA^Ntr) compose a branch of the system alien to sugar traffic but thought to have an influence in coordination of N vs. C metabolism. We have used a genetic approach to clarify the course of high-energy phosphate through this reduced set of PTS proteins. To this end, we have monitored the phosphorylation state in vivo of the EIIA^Ntr enzyme in various genetic backgrounds and growth conditions. Our results show that the source of phosphate available to the system is phosphoenolpyruvate (PEP) and that the prime flow of phosphate through the N/C-sensing PTS proceeds PEP ^TM EI^{Ntr TM} NPr ^TM EIIA^Ntr. We also found that in the presence of fructose -unlike with succinate- EIIA^Ntr can be phosphorylated in a ptsP strain but not in a double ptsP fruB mutant. This result revealed that the fructose transport system has the ability of cross-talking in vivo with the N-related PTS branch. The data reported here thus document an unexpected connection in vivo between sugar-dependent and sugar-independent PTS systems.