Characterization of the catalytic activities of the PhoQ histidine protein kinase of Salmonella enterica serovar Typhimurium.
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Montagne M, Martel A, Le Moual H
Characterization of the catalytic activities of the PhoQ histidine protein kinase of Salmonella enterica serovar Typhimurium.
J Bacteriol. 2001 Mar;183(5):1787-91.
- PubMed ID
- 11160113 [ View in PubMed]
- 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.