Characterization of the catalytic activities of the PhoQ histidine protein kinase of Salmonella enterica serovar Typhimurium.
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.
Montagne
M
M
Department of Pharmacology, Faculty of Medicine, Université de Sherbrooke, Sherbrooke, Québec, Canada J1H 5N4.
Martel
A
A
Le Moual
H
H
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
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