title: Solution structure of NPr, a bacterial signal-transducing protein that controls the phosphorylation state of the potassium transporter-regulating protein IIA Ntr.
abstract: A nitrogen-related signal transduction pathway, consisting of the three phosphotransfer proteins EI(Ntr), NPr, and IIA(Ntr), was discovered recently to regulate the uptake of K(+) in Escherichia coli. In particular, dephosphorylated IIA(Ntr) inhibits the activity of the K(+) transporter TrkA. Since the phosphorylation state of IIA(Ntr) is partially determined by its reversible phosphorylation by NPr, we have determined the three-dimensional structure of NPr by solution NMR spectroscopy. In total, we obtained 973 NOE-derived distance restraints, 112 chemical shift-derived backbone angle restraints, and 35 hydrogen-bond restraints derived from temperature coefficients (wave). We propose that temperature wave is useful for identifying exposed beta-strands and assists in establishing protein folds based on chemical shifts. The deduced structure of NPr contains three alpha-helices and four beta-strands with the three helices all packed on the same face of the beta-sheet. The active site residue His16 of NPr for phosphoryl transfer was found to be neutral and in the N epsilon 2-H tautomeric state. There appears to be increased motion in the active site region of NPr compared to HPr, a homologous protein involved in the uptake and regulation of carbohydrate utilization.
authors.affiliation: Eppley Institute for Research in Cancer and Allied Diseases, University of Nebraska Medical Center, 986805 Nebraska Medical Center, Omaha, NE 68198-6805, USA.
authors.forename: Xia
authors.initials: X
authors.lastname: Li
authors.forename: Alan
authors.initials: A
authors.lastname: Peterkofsky
authors.forename: Guangshun
authors.initials: G
authors.lastname: Wang
mesh_terms: D001665:Binding Sites; D002352:Carrier Proteins / Q000737:chemistry*; D004926:Escherichia coli / Q000737:chemistry / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000378:metabolism; D006639:Histidine / Q000737:chemistry; D019906:Nuclear Magnetic Resonance, Biomolecular; D010455:Peptides / Q000737:chemistry; D028044:Phosphate-Binding Proteins; D010731:Phosphoenolpyruvate Sugar Phosphotransferase System / Q000378:metabolism; D010766:Phosphorylation; D011188:Potassium / Q000378:metabolism
chemical_list: D002352:Carrier Proteins; D029968:Escherichia coli Proteins; C502371:NPr protein, E coli; D010455:Peptides; D028044:Phosphate-Binding Proteins; D006639:Histidine; C487562:IIA(Ntr) protein, E coli; D010731:Phosphoenolpyruvate Sugar Phosphotransferase System; D011188:Potassium