Affiliation:
1. Department of Pharmacology, Faculty of Medicine, Université de Sherbrooke, Sherbrooke, Québec, Canada J1H 5N4
Abstract
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 Mg
2+
, Mn
2+
, Ca
2+
, or Ba
2+
resulted in PhoQ autophosphorylation. However, when Mg
2+
or Mn
2+
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 Mg
2+
or Mn
2+
was present at high concentrations. The instability of purified [
32
P]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 Mg
2+
concentration. These data are consistent with a model in which Mg
2+
binding to the sensory domain of PhoQ coordinately regulates autokinase and phosphatase activities.
Publisher
American Society for Microbiology
Subject
Molecular Biology,Microbiology
Cited by
52 articles.
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