TY - JOUR
T1 - Modulation of KdpD phosphatase implicated in the physiological expression of the Kdp ATPase of Escherichia coli
AU - Brandon, Lauren
AU - Dorus, Steve
AU - Epstein, Wolfgang
AU - Altendorf, Karlheinz
AU - Jung, Kirsten
PY - 2000
Y1 - 2000
N2 - The KdpD sensor kinase and the KdpE response regulator control the expression of the kdpFABC operon, encoding the KdpFABC high-affinity K+ transport system of Escherichia coli. Low turgor pressure has been postulated to be the environmental stimulus to express KdpFABC. KdpD has autokinase, phosphotransferase and, like many sensor kinases, response regulator (phospho-KdpE) specific phosphatase activity. To determine which of these activities are altered in response to the environmental stimulus, we isolated and analysed six kdpD mutants that cause constitutive expression of KdpFABC. In three of the mutants, phosphatase activity was undetectable and, in two, phosphatase was reduced. Kinase activity was unaffected in four of the mutants, but elevated in one. In one mutant, a pseudorevertant of a kdpD null mutation, kinase and phosphatase were both reduced to 20% of the wild-type level. These findings suggest that initiation of signal transduction by KdpD is mediated by the inhibition of the phospho-KdpE-specific phosphatase activity of KdpD, leading to an accumulation of phospho-KdpE, which in turn activates the expression of the KdpFABC system. The data also suggest that levels of activity in vitro may differ from what occurs in vivo, because in vitro conditions cannot replicate those in vivo.
AB - The KdpD sensor kinase and the KdpE response regulator control the expression of the kdpFABC operon, encoding the KdpFABC high-affinity K+ transport system of Escherichia coli. Low turgor pressure has been postulated to be the environmental stimulus to express KdpFABC. KdpD has autokinase, phosphotransferase and, like many sensor kinases, response regulator (phospho-KdpE) specific phosphatase activity. To determine which of these activities are altered in response to the environmental stimulus, we isolated and analysed six kdpD mutants that cause constitutive expression of KdpFABC. In three of the mutants, phosphatase activity was undetectable and, in two, phosphatase was reduced. Kinase activity was unaffected in four of the mutants, but elevated in one. In one mutant, a pseudorevertant of a kdpD null mutation, kinase and phosphatase were both reduced to 20% of the wild-type level. These findings suggest that initiation of signal transduction by KdpD is mediated by the inhibition of the phospho-KdpE-specific phosphatase activity of KdpD, leading to an accumulation of phospho-KdpE, which in turn activates the expression of the KdpFABC system. The data also suggest that levels of activity in vitro may differ from what occurs in vivo, because in vitro conditions cannot replicate those in vivo.
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U2 - 10.1046/j.1365-2958.2000.02219.x
DO - 10.1046/j.1365-2958.2000.02219.x
M3 - Article
C2 - 11123681
AN - SCOPUS:0034537416
SN - 0950-382X
VL - 38
SP - 1086
EP - 1092
JO - Molecular Microbiology
JF - Molecular Microbiology
IS - 5
ER -