title: Stimulation of the potassium sensor KdpD kinase activity by interaction with the phosphotransferase protein IIA(Ntr) in Escherichia coli.
abstract: 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.
authors.affiliation: Georg-August-Universität Göttingen, Abteilung für Allgemeine Mikrobiologie, Institut für Mikrobiologie und Genetik, Grisebachstrasse 8, D-37077 Göttingen, Germany.
authors.forename: Denise
authors.initials: D
authors.lastname: Lüttmann
authors.forename: Ralf
authors.initials: R
authors.lastname: Heermann
authors.forename: Björn
authors.initials: B
authors.lastname: Zimmer
authors.forename: Antje
authors.initials: A
authors.lastname: Hillmann
authors.forename: Isabella Sofia
authors.initials: IS
authors.lastname: Rampp
authors.forename: Kirsten
authors.initials: K
authors.lastname: Jung
authors.forename: Boris
authors.initials: B
authors.lastname: Görke
mesh_terms: D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial; D016296:Mutagenesis; D009876:Operon; D010731:Phosphoenolpyruvate Sugar Phosphotransferase System / Q000378:metabolism*; D010766:Phosphorylation; D011188:Potassium / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D011494:Protein Kinases / Q000378:metabolism*
chemical_list: D029968:Escherichia coli Proteins; C489580:KdpD protein, E coli; D011494:Protein Kinases; C487562:IIA(Ntr) protein, E coli; D010731:Phosphoenolpyruvate Sugar Phosphotransferase System; D011188:Potassium