Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.7.13.3 (histidine kinase)
 2,405 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Signal transduction in the bacterial Omp, Che, and Ntr systems involves the phosphorylation and dephosphorylation of response regulators (OmpR, CheY and CheB, NRI) that share a homologous domain. We show that in the Omp system, the transmembrane sensor EnvZ, catalyzes both the phosphorylation of OmpR and the dephosphorylation of OmpR-P. The phosphorylation reaction proceeds by a mechanism shared with the Ntr and Che kinases, NRII, and CheA. EnvZ can phosphorylate NRI and can stimulate transcription from the glnAp2 promoter, and similarly, CheA can phosphorylate OmpR and can stimulate transcription from the ompF promoter. OmpR-P formed by either CheA or EnvZ is much more stable than CheY-P and NRI-P, but is rapidly hydrolyzed to OmpR and Pi by EnvZ in the presence of ATP, ADP, or nonhydrolyzable analogs of ATP. Because EnvZ is normally a transmembrane receptor with a periplasmic sensory domain, our results suggest that the role of EnvZ may be to control the intracellular concentration of OmpR-P in response to environmental signals.
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PMID:Phosphorylation and dephosphorylation of a bacterial transcriptional activator by a transmembrane receptor. 255 46

EnvZ of Escherichia coli is a transmembrane histidine kinase belonging to the family of two-component signal transducing systems prevalent in prokaryotes and recently discovered in eukaryotes. In response to changes in medium osmolarity EnvZ regulates the level of phosphorylated OmpR, its conjugate response-regulating transcription factor for ompF and ompC genes. EnvZ has dual opposing enzymatic activities; OmpR-phosphorylase (kinase) and phospho-OmpR-dephosphorylase (phosphatase). The osmotic signal is proposed to regulate the ratio of the kinase to the phosphatase activities of EnvZ to modulate the level of OmpR phosphorylation. In this work we used a COOH-terminal fragment of a previously identified kinase-/phosphatase+ EnvZ mutant (EnvZ-N347D) to demonstrate that the phosphoryl group on phospho-OmpR is transferred back to EnvZ to the same histidine residue (His243) that is utilized for the autokinase reaction by the wild type protein. Phospho-EnvZ-N347D thus formed could also transfer its phosphoryl group back to OmpR. The phosphotransfer reaction from phospho-OmpR to EnvZ.N347D was inhibited by ADP while Mg2+ ions stimulated the dephosphorylation reaction, resulting in release of inorganic phosphate. These results indicate that the energy levels of phosphoryl groups on OmpR and EnvZ are very similar and that the phosphatase reaction in the EnvZ.N347D mutant involves a reversal of the phosphotransfer reaction from EnvZ to OmpR using the identical His243 residue.
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PMID:Reverse phosphotransfer from OmpR to EnvZ in a kinase-/phosphatase+ mutant of EnvZ (EnvZ.N347D), a bifunctional signal transducer of Escherichia coli. 857 33

Kinase A is the sensor histidine kinase responsible for processing postexponential phase information and providing phosphate input to the phosphorelay that activates developmental transcription via phosphorylated Spo0A. A protein inhibitor, KipI, of kinase A was discovered encoded in an operon of genes of unknown function but regulated by the availability of fixed nitrogen. KipI is a potent inhibitor of the autophosphorylation reaction of kinase A but does not inhibit phosphate transfer to the Spo0F response regulator once kinase A is phosphorylated. KipI is an inhibitor of the catalytic domain of kinase A affecting the ATP/ADP reactions and not the phosphotransferase functions of this domain. The inhibitory activity of KipI is counteracted by the product of another gene in the operon, KipA. This protein may bind to KipI, preventing its function as an inhibitor of kinase A. KipI may be the first representative of a new class of signal transduction inhibitors that function by direct interaction with the catalytic domain of histidine kinases to counteract signals influencing the "sensor" domain of such kinases. This inhibitor represents yet another way by which the phosphorelay signal transduction system is affected by negative regulators under the control of metabolic, environmental, or cell cycle influences antithetical to the initiation of developmental transcription.
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PMID:A novel histidine kinase inhibitor regulating development in Bacillus subtilis. 933 21

Recent drug screenings for new antibacterial drugs directed against histidine phospho-relay signalling pathways in bacteria have resulted in compounds which potently inhibit the histidine kinase activity of bacterial two-component systems. The present study demonstrates that one of these compounds, LY266500, is also a potent inhibitor of histidine phosphorylation in the unicellular eukaryotic parasite Trypanosoma brucei, both in vitro and in whole cells. In vitro, it inhibits histidine phosphorylation of mitochondrial succinyl CoA synthetase. LY26650 does not interfere with the phosphotransfer from the histidine-phosphorylated protein to ADP. In standardized cell culture tests, LY266500 potently inhibits the proliferation of the human pathogens T. brucei rhodesiense and Leishmania donovani. Since the inhibitory activity in vivo is life-cycle stage specific and correlates well with the mitochondrial activity in the different stages, the effect of LY266500 is most likely due to its specific inhibition of the mitochondrial succinyl CoA synthetase.
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PMID:Inhibition of succinyl CoA synthetase histidine-phosphorylation in Trypanosoma brucei by an inhibitor of bacterial two-component systems. 1037 93

Most histidine kinases are bifunctional enzymes having both kinase and phosphatase activities. The cytoplasmic kinase domain of EnvZ, a transmembrane histidine kinase functioning as an osmosensor in Escherichia coli, consists of two distinct functional subdomains: domain A [EnvZc(223-289)] and domain B [EnvZc(290-450)]. NMR studies demonstrated that domain A consists of a four-helix bundle serving as a dimerization and phosphotransfer domain, and domain B functions as the ATP-binding and catalytic domain. Here we demonstrate that domain A by itself has the phosphatase activity both in vitro and in vivo. This phosphatase activity is Mg(2+) dependent but is not activated by ADP, ATP, or adenosine 5'-[beta, gamma-imido]triphosphate (AMPPNP), each of which may serve as a cofactor for the EnvZ phosphatase activity. Domain B showed a small but distinct effect on the domain A phosphatase activity only in the presence of ADP or AMPPNP. However, when domain B was covalently linked to domain A, dramatic cofactor-dependent enhancement of the phosphatase activity was observed. Extending domain A for another 75 residues at the C terminus or 44 residues at the N terminus did not enhance its phosphatase activity. Substitution mutations at His-243, the autophosphorylation site, demonstrate that the His residue plays an essential role in the phosphatase activity. The so-called X-region mutant L288P that is known to specifically abolish the phosphatase activity in EnvZ had no effect on the domain A phosphatase function. We propose that the EnvZ phosphatase activity is regulated by relative positioning of domains A and B, which is controlled by external signals. We also propose that the His-243 residue participates in both kinase and phosphatase reactions.
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PMID:Phosphatase activity of histidine kinase EnvZ without kinase catalytic domain. 1088 12

To probe the structural basis for protein histidine kinase (PHK) catalytic activity and the prospects for PHK-specific inhibitor design, we report the crystal structures for the nucleotide binding domain of Thermotoga maritima CheA with ADP and three ATP analogs (ADPNP, ADPCP and TNP-ATP) bound with either Mg(2+) or Mn(2+). The conformation of ADPNP bound to CheA and related ATPases differs from that reported in the ADPNP complex of PHK EnvZ. Interactions of the active site with the nucleotide gamma-phosphate and its associated Mg(2+) ion are linked to conformational changes in an ATP-lid that could mediate recognition of the substrate domain. The inhibitor TNP-ATP binds CheA with its phosphates in a nonproductive conformation and its adenine and trinitrophenyl groups in two adjacent binding pockets. The trinitrophenyl interaction may be exploited for designing CheA-targeted drugs that would not interfere with host ATPases.
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PMID:Nucleotide binding by the histidine kinase CheA. 1127 58

Nucleoside-diphosphate (NDP) kinase (NTP:nucleoside-diphosphate phosphotransferase) catalyzes the reversible transfer of gamma-phosphates from nucleoside triphosphates to nucleoside diphosphates through an invariant histidine residue. It has been reported that the high-energy phosphorylated enzyme intermediate exhibits a protein phosphotransferase activity toward the protein histidine kinases CheA and EnvZ, members of the two-component signal transduction systems in bacteria. Here we demonstrate that the apparent protein phosphotransferase activity of NDP kinase occurs only in the presence of ADP, which can mediate the phosphotransfer from the phospho-NDP kinase to the target enzymes in catalytic amounts (approximately 1 nm). These findings suggest that the protein kinase activity of NDP kinase is probably an artifact attributable to trace amounts of contaminating ADP. Additionally, we show that Escherichia coli NDP kinase, like its human homologue NM23-H2/PuF/NDP kinase B, can bind and cleave DNA. Previous in vivo functions of E. coli NDP kinase in the regulation of gene expression that have been attributed to a protein phosphotransferase activity can be explained in the context of NDP kinase-DNA interactions. The conservation of the DNA binding and DNA cleavage activities between human and bacterial NDP kinases argues strongly for the hypothesis that these activities play an essential role in NDP kinase function in vivo.
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PMID:Interactions between Escherichia coli nucleoside-diphosphate kinase and DNA. 1174 5

Histidine kinase EnvZ, a transmembrane osmotic sensor for Escherichia coli, is a bifunctional enzyme having OmpR (its cognate response regulator) kinase and phosphorylated OmpR (OmpR-P) phosphatase activities. Its cytoplasmic domain consists of domain A responsible for dimerization of EnvZ, histidine phosphotransfer and phosphatase activities, and domain B responsible for ATP binding. Here, we have constructed a number of substitution mutations at the G2 box, one of the conserved motifs in domain B, and demonstrated that they influence the phosphatase activity of EnvZ over a wide range. The effects of ADP, a cofactor for the phosphatase activity, were found to be substantially different depending upon the mutations. The effects of these mutations were also examined in vivo using a chimeric Tar-EnvZ construct (Taz1-1), and the results agreed with the in vitro data for the phosphatase and kinase activities for all mutations. Using Taz1-1 carrying the T402A mutation, three independent intragenic suppressor mutations (T235M, S269L and E276K) were isolated, and all were found in domain A. Together, the present results demonstrate for the first time that domain A and domain B are functionally co-ordinated and topologically arranged in a specific manner. The G2 box may modulate the interaction between these two domains in response to extracellular osmolarity.
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PMID:The role of the G2 box, a conserved motif in the histidine kinase superfamily, in modulating the function of EnvZ. 1213 13

Hexokinase deficiency is a rare autosomal recessive disease with a clinical phenotype of severe hemolysis. We report a novel homozygous missense mutation in exon 15 (c.2039C>G, HK [hexokinase] Utrecht) of HK1, the gene that encodes red blood cell-specific hexokinase-R, in a patient previously diagnosed with hexokinase deficiency. The Thr680Ser substitution predicted by this mutation affects a highly conserved residue in the enzyme's active site that interacts with phosphate moieties of adenosine diphosphate, adenosine triphosphate (ATP), and inhibitor glucose-6-phosphate. We correlated the molecular data to the severe clinical phenotype of the patient by means of altered enzymatic properties of partially purified hexokinase from the patient, notably with respect to Mg(2+)-ATP binding. These kinetic properties contradict those obtained from a recombinant mutant brain hexokinase-I with the same Thr680Ser substitution. This contradiction thereby stresses the valuable contribution of studying patients with hexokinase deficiency to achieve a better understanding of hexokinase's key role in glycolysis.
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PMID:HK Utrecht: missense mutation in the active site of human hexokinase associated with hexokinase deficiency and severe nonspherocytic hemolytic anemia. 1239 45

EnvZ is a histidine protein kinase important for osmoregulation in bacteria. While structural data are available for this enzyme, the nucleotide binding pocket is not well characterized. The ATP binding domain (EnvZB) was expressed, and its ability to bind nucleotide derivatives was assessed using equilbrium and stopped-flow fluorescence spectroscopy. The fluorescence emission of the trinitrophenyl derivatives, TNP-ATP and TNP-ADP, increase upon binding to EnvZB. The fluorescence enhancements were quantitatively abolished in the presence of excess ADP, indicating that the fluorescent probes occupy the nucleotide binding pocket. Both TNP-ATP and TNP-ADP bind to EnvZB with high affinity (K(d) = 2-3 microM). The TNP moiety attached to the ribose ring does not impede access of the fluorescent nucleotide into the binding pocket. The association rate constant for TNP-ADP is 7 microM(-1) s(-1), a value consistent with those for natural nucleotides and the eucaryotic protein kinases. Using competition experiments, it was found that ATP and ADP bind 30- and 150-fold more poorly, respectively, than the corresponding TNP-derivatized forms. Surprisingly, the physiological metal Mg(2+) is not required for ADP binding and only enhances ATP affinity by 3-fold. Although portions of the nucleotide pocket are disordered, the recombinant enzyme is highly stable, unfolding only at temperatures in excess of 70 degrees C. The unusually high affinity of the TNP derivatives compared to the natural nucleotides suggests that hydrophobic substitutions on the ribose ring enforce an altered binding mode that may be exploited for drug design strategies.
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PMID:Probing the nucleotide binding domain of the osmoregulator EnvZ using fluorescent nucleotide derivatives. 1243 44


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