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Stimulation of the potassium sensor KdpD kinase activity by interaction with the phosphotransferase protein IIA Ntr in Escherichia coli
Author(s) -
Lüttmann Denise,
Heermann Ralf,
Zimmer Björn,
Hillmann Antje,
Rampp Isabella Sofia,
Jung Kirsten,
Görke Boris
Publication year - 2009
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/j.1365-2958.2009.06704.x
Subject(s) - pep group translocation , biology , dephosphorylation , phosphotransferase , escherichia coli , phosphoenolpyruvate carboxykinase , kinase , biochemistry , phosphorylation , response regulator , transporter , glucose transporter , phosphatase , enzyme , gene , mutant , endocrinology , insulin
Summary Proteins EI Ntr , NPr and IIA Ntr form a phosphoryl group transfer chain (Ntr‐PTS) working in parallel to the phosphoenolpyruvate:carbohydrate phosphotransferase system (transport‐PTS) in Escherichia coli . Recently, it was shown that dephosphorylated IIA Ntr binds and inhibits TrkA, a low‐affinity potassium transporter. Here we report that the Ntr‐PTS also regulates expression of the high‐affinity K + transporter KdpFABC, which rescues K + uptake at limiting K + concentrations. Transcription initiation at the kdpFABC promoter is positively controlled by the two‐component system KdpD/KdpE in response to K + availability. We found that kdp promoter activity is stimulated by the dephosphorylated form of IIA Ntr . Two‐hybrid data and biochemical analysis revealed that IIA Ntr interacts with sensor kinase KdpD and stimulates kinase activity, resulting in increased levels of phosphorylated response regulator KdpE. The data suggest that exclusively dephosphorylated IIA Ntr binds and activates KdpD. As there is cross‐talk between the Ntr‐PTS and the transport‐PTS, carbon source utilization affects kdpFABC expression. Expression is enhanced, when cells utilize preferred carbohydrates like glucose, which results in preferential dephosphorylation of the transport‐PTS and also of IIA Ntr . Taken together, the data show that the Ntr‐PTS has an important role in maintaining K + homeostasis and links K + uptake to carbohydrate metabolism.