title: Characterization of the catalytic activities of the PhoQ histidine protein kinase of Salmonella enterica serovar Typhimurium.
abstract: Studies of Escherichia coli membranes that were highly enriched in the Salmonella enterica serovar Typhimurium PhoQ protein showed that the presence of ATP and divalent cations such as Mg2+, Mn2+, Ca2+, or Ba2+ resulted in PhoQ autophosphorylation. However, when Mg2) or Mn2+ was present at concentrations higher than 0.1 mM, the kinetics of PhoQ autophosphorylation were strongly biphasic, with a rapid autophosphorylation phase followed by a slower dephosphorylation phase. A fusion protein lacking the sensory and transmembrane domains retained the autokinase activity but could not be dephosphosphorylated when Mg2+ or Mn2+ was present at high concentrations. The instability of purified [32P]phospho-PhoP in the presence of PhoQ-containing membranes indicated that PhoQ also possesses a phosphatase activity. The PhoQ phosphatase activity was stimulated by increasing the Mg2+ concentration. These data are consistent with a model in which Mg2+ binding to the sensory domain of PhoQ coordinately regulates autokinase and phosphatase activities.
authors.affiliation: Department of Pharmacology, Faculty of Medicine, Université de Sherbrooke, Sherbrooke, Québec, Canada J1H 5N4.
authors.forename: M
authors.initials: M
authors.lastname: Montagne
authors.forename: A
authors.initials: A
authors.lastname: Martel
authors.forename: H
authors.initials: H
authors.lastname: Le Moual
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism*; D002413:Cations, Divalent / Q000378:metabolism; D002462:Cell Membrane / Q000201:enzymology; D004795:Enzyme Stability; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D000071677:Histidine Kinase; D010710:Phosphates / Q000378:metabolism; D010744:Phosphoric Monoester Hydrolases / Q000378:metabolism; D010766:Phosphorylation; D011494:Protein Kinases / Q000235:genetics* / Q000378:metabolism*; D012486:Salmonella typhimurium / Q000201:enzymology* / Q000235:genetics
chemical_list: D001426:Bacterial Proteins; D002413:Cations, Divalent; C079792:PhoQ protein, Bacteria; D010710:Phosphates; C061064:PhoP protein, Bacteria; D011494:Protein Kinases; D000071677:Histidine Kinase; D010744:Phosphoric Monoester Hydrolases