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PTS regulation of ABC transporters
The carbohydrate phosphotransferase system (PTS) is the key signal transduction pathway involved in the regulation of carbon metabolism in Gram-negative and Gram-positive bacteria. This PTS system acquires phosphate from phosphoenol pyruvate (PEP) and passes it through the components of the system to the ultimate acceptor, a sugar from the environment, which is phosphorylated upon transport by membrane components EIIB and EIIC. In Gram-negative bacteria, PTSNtr represents an alternative PTS system encoded by the genes ptsP (EINtr), ptsO (Npr) and ptsN (EIINtr), preserving the phosphotransfer components, but lacking the membrane permeases. The absence of components directly involved in solute translocation suggests an exclusively regulatory role. Additionally, this system is linked to nitrogen (N) metabolism as ptsO and ptsN are usually adjacent to rpoN (encoding the N sigma factor, σ54), e.g. in E. coli.
In R. leguminosarum PTSNtr is a phosphotransferase system that globally regulates ATP-binding cassette (ABC) transport systems (Prell et al., 2012: Molecular Microbiology 84:117-129) and has been demonstrated to inactivate ABC transport under potassium limitation (Untiet et al. 2013, PLoS One 8(5):e64682). Our objective is to determine the phosphotransfer pathway between PTSNtr components, confirming their physical interactions and elucidating the phosphorelay cascade. In addition, we wish to characterize the fine-tuned regulation exerted by PTSNtr proteins over essential processes for the survival of the cell, such as the response to osmotic stress and nutrient uptake. As PTSNtr is not only widely distributed in bacteria but also constitutes an essential regulatory system in Rhizobium, in uncovering the role of PTSNtr we would identify one of the most important regulatory mechanisms in bacterial physiology and growth.
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