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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)

The production of lipase and protease from psychrotrophic strains of Pseudomonas fluorescens may result in spoilage of dairy products. The lipase (lipA) and alkaline metalloprotease (aprX) genes of P. fluorescens B52 are regulated by temperature and are located at opposite ends of an operon which contains eight genes and spans 14 kb. In this report, we show that lipase activity in the supernatant of cultures of P. fluorescens strain B52 is also regulated by the homologue of the Escherichia coli EnvZ-OmpR two-component regulatory system. Differences in the regulation of lipase and protease may be related to the proximal and distal locations of aprX and lipA within the operon.
FEMS Microbiol Lett 2004 Dec 15
PMID:Regulation of the aprX-lipA operon of Pseudomonas fluorescens B52: differential regulation of the proximal and distal genes, encoding protease and lipase, by ompR-envZ. 1559 39

Protein phosphorylation is one of the most ubiquitous and important types of post-translational modification for the regulation of cell function. The importance of two-component histidine kinases in bacteria, fungi and plants has long been recognised. In mammals, the regulatory roles of serine/threonine and tyrosine kinases have attracted most attention. However, the existence of histidine kinases in mammalian cells has been known for many years, although little is still understood about their biological roles by comparison with the hydroxyamino acid kinases. In addition, with the exception of NDP kinase, other mammalian histidine kinases remain to be identified and characterised. NDP kinase is a multifunctional enzyme that appears to act as a protein histidine kinase and as such, to regulate the activation of some G-proteins. Histone H4 histidine kinase activity has been shown to correlate with cellular proliferation and there is evidence that it is an oncodevelopmental marker in liver. This review mainly concentrates on describing recent research on these two types of histidine kinase. Developments in methods for the detection and assay of histidine kinases, including mass spectrometric methods for the detection of phosphohistidines in proteins and in-gel kinase assays for histone H4 histidine kinases, are described. Little is known about inhibitors of mammalian histidine kinases, although there is much interest in two-component histidine kinase inhibitors as potential antibiotics. The inhibition of a histone H4 histidine kinase by genistein is described and that of two-component histidine kinase inhibitors of structurally-related mammalian protein kinases. In addition, recent findings concerning mammalian protein histidine phosphatases are briefly described.
Biochim Biophys Acta 2005 Dec 30
PMID:Mammalian histidine kinases. 1618 7

Bacterial histidine kinases have been proposed as targets for the discovery of new antibiotics, yet few specific inhibitors of bacterial histidine kinases have been reported. We report here a novel thienopyridine (TEP) compound that inhibits bacterial histidine kinases competitively with respect to ATP but does not comparably inhibit mammalian serine/threonine kinases. Although it partitions into membranes and does not inhibit the growth of bacterial or mammalian cells, TEP could serve as a starting compound for a new class of histidine kinase inhibitors with antibacterial activity.
J Bacteriol 2005 Dec
PMID:New class of competitive inhibitor of bacterial histidine kinases. 1629 94

Phytochromes (Phys) comprise a superfamily of red-/far-red-light-sensing proteins. Whereas higher-plant Phys that control numerous growth and developmental processes have been well described, the biochemical characteristics and functions of the microbial forms are largely unknown. Here, we describe analyses of the expression, regulation, and activities of two Phys in the filamentous fungus Neurospora crassa. In addition to containing the signature N-terminal domain predicted to covalently associate with a bilin chromophore, PHY-1 and PHY-2 contain C-terminal histidine kinase and response regulator motifs, implying that they function as hybrid two-component sensor kinases activated by light. A bacterially expressed N-terminal fragment of PHY-2 covalently bound either biliverdin or phycocyanobilin in vitro, with the resulting holoprotein displaying red-/far-red-light photochromic absorption spectra and a photocycle in vitro. cDNA analysis of phy-1 and phy-2 revealed two splice isoforms for each gene. The levels of the phy transcripts are not regulated by light, but the abundance of the phy-1 mRNAs is under the control of the circadian clock. Phosphorylated and unphosphorylated forms of PHY-1 were detected; both species were found exclusively in the cytoplasm, with their relative abundances unaffected by light. Strains containing deletions of phy-1 and phy-2, either singly or in tandem, were not compromised in any known photoresponses in Neurospora, leaving their function(s) unclear.
Eukaryot Cell 2005 Dec
PMID:Genetic and molecular analysis of phytochromes from the filamentous fungus Neurospora crassa. 1633 31

Phytochromes are light-sensing macromolecules that are part of a two component phosphorelay system controlling gene expression. Photoconversion between the Pr and Pfr forms facilitates autophosphorylation of a histidine in the dimerization domain (DHp). We report the low-resolution structure of a bacteriophytochrome (Bph) in the catalytic (CA) Pr form in solution determined by small-angle X-ray scattering (SAXS). Ab initio modeling reveals, for the first time, the domain organization in a typical bacteriophytochrome, comprising an chromophore binding and phytochrome (PHY) N terminal domain followed by a C terminal histidine kinase domain. Homologous high-resolution structures of the light-sensing chromophore binding domain (CBD) and the cytoplasmic part of a histidine kinase sensor allows us to model 75% of the structure with the remainder comprising the phytochrome domain which has no 3D representative in the structural database. The SAXS data reveal a dimeric Y shaped macromolecule and the relative positions of the chromophores (biliverdin), autophosphorylating histidine residues and the ATP molecules in the kinase domain. SAXS data were collected from a sample in the autophosphorylating Pr form and reveal alternate conformational states for the kinase domain that can be modeled in an open (no-catalytic) and closed (catalytic) state. This model suggests how light-induced signal transduction can stimulate autophosphorylation followed by phosphotransfer to a response regulator (RR) in the two-component system.
J Mol Biol 2006 Dec 08
PMID:Small-angle X-ray scattering reveals the solution structure of a bacteriophytochrome in the catalytically active Pr state. 1702 28

In anaerobiosis, Escherichia coli can use trimethylamine N-oxide (TMAO) as a terminal electron acceptor. Reduction of TMAO in trimethylamine (TMA) is mainly performed by the respiratory TMAO reductase. This system is encoded by the torCAD operon, which is induced in the presence of TMAO. This regulation involves a two-component system comprising TorS, an unorthodox histidine kinase, and TorR, a response regulator. A third protein, TorT, sharing homologies with periplasmic binding proteins, plays a key role in this regulation because disruption of the torT gene abolishes tor expression. In this study we showed that TMAO protects TorT against degradation by the GluC endoproteinase and modifies its temperature-induced CD spectrum. We also isolated a TorT negative mutant that is no longer protected by TMAO from degradation by GluC. Isothermal titration calorimetry confirmed that TorT binds TMAO with a binding constant of 150 mum. Therefore, we conclude that TorT binds TMAO and that this binding promotes a conformational change of TorT. We also showed that TorT interacts with the periplasmic domain of TorS in both the presence and absence of TMAO but the TorT-TMAO complex induces a higher GluC protection of TorS than TorT alone. These results support the idea that TMAO binding to TorT induces a cascade of conformational changes from TorT to TorS, leading to TorS activation. We identified several homologues of the TorT protein that define a new family of periplasmic binding proteins. We thus propose that the members of this family bind TMAO or related compounds and that they are involved in signal transduction or even substrate transport.
J Biol Chem 2006 Dec 15
PMID:TorT, a member of a new periplasmic binding protein family, triggers induction of the Tor respiratory system upon trimethylamine N-oxide electron-acceptor binding in Escherichia coli. 1704 Sep 9

Nitrate transport activity of the LtnT permease of the cyanobacterium Synechococcus elongatus is activated when LtnA, a response regulator without an effector domain, is phosphorylated by LtnB, a hybrid histidine kinase. We identified a protein (LtnC) that is required for activation of LtnT. LtnC consists of an N-terminal histidine-containing phosphoacceptor (HisKA) domain, a receiver domain, and a unique C-terminal domain found in some cyanobacterial proteins. Because LtnC lacks an ATP-binding kinase domain of a histidine kinase, it is incapable of autophosphorylation, but LtnC is phosphorylated by LtnA. The histidine residue in the HisKA domain but not the aspartate residue in the receiver domain is essential for phosphorylation of LtnC and activation of LtnT. LtnC phosphorylation leads to oligomerization of the protein. Fusion of the C-terminal domain of LtnC to glutathione S-transferase, which forms oligomers, also activates LtnT, suggesting that oligomerization of the LtnC C-terminal domain causes LtnT activation. These results indicate that the C-terminal domain of LtnC acts as an effector domain that directs the output of the signal from the phosphorelay system. The two-step (His-Asp-His) phosphorelay system, composed of the LtnB, LtnA, and LtnC proteins, is distinct from the known phosphorelay systems, namely, the typical two-component system (His-Asp) and the multistep phosphorelay system (His-Asp-His-Asp), because the HisKA domain of LtnC is the terminal phosphoacceptor that determines the signal output. LtnC is a new class of signal transducer in His-Asp phosphorelay systems that contains a HisKA domain and an effector domain.
J Biol Chem 2006 Dec 08
PMID:A new class of signal transducer in His-Asp phosphorelay systems. 1704 Sep 12

Gladiolus is an ethylene insensitive flower whose exogenous ethylene and ethylene inhibitors have no effect on the petal senescence process. To study which processes in gladiolus are associated with changes in ethylene perception, two types of gladiolus genes, named GgERS1a and GgERS1b, respectively, homologous to the Arabidopsis ethylene receptor gene ERS1 were isolated. GgERS1a is conserved in terms of exon numbers and intron positions, whereas GgERS1b is almost same with GgERS1a except lacking 636 nucleotide encoding first and second histidine kinase (HisKA) motifs. The sequence data on full length genomic DNA indicated that both GgERS1a and b were spliced from different genomic DNA. As the result of mRNA expression study, in spite of lacking the two significant motifs, the expression of GgERS1b dramatically changed with advance in petal senescence, whereas the level of GgERS1a expressed highly and constitutively. The result suggests that both the genes possess a significant role for the subfunctionalization process to provide ethylene insensitivity in gladiolus flowers.
Biochem Biophys Res Commun 2006 Dec 22
PMID:A novel ethylene receptor homolog gene isolated from ethylene-insensitive flowers of gladiolus (Gladiolus grandiflora hort.). 1708 12

Photoactivation of hypericin is known to generate reactive oxygen species and induce phototoxic effects. However, modulation of the cellular antioxidant defense would influence the extent and severity of the photodynamic effects. We have previously shown that hypericin-mediated photodynamic therapy (PDT) induced a significant reduction of Glutathione S-transferase activity. In this study, we investigated the phototoxic effects of hypericin-mediated PDT in nasopharyngeal cancer (NPC) in vitro and analyzed the expression of metallothionein (MT), a family of potential free radical scavengers. HK1 NPC cells were subjected to PDT treatment in vitro, and the effects on cell death were analyzed by flow cytometry (using propidium iodide and Annexin V staining) and transmission electron microscopy. The expression profile of MT-1E and MT-2A isoforms (the only functional MT isoforms expressed in HK1 NPC cells) were determined by quantitative real-time RT-PCR. The results showed that hypericin PDT induced necrotic cell death as evidenced by the absence of a subdiploid peak and decreased Annexin-V fluorescence. Ultrastructural examination verified the presence of cell necrosis. There was a significant up-regulation of MT-1E and MT-2A isoforms six hours following PDT, with an approximately 50-fold rise in the expression level of MT-1E and a 15-fold increase of MT-2A. Hence, despite the up-regulation of MT, cells still succumbed to PDT-induced necrosis. It appears that the oxidative stress induced by PDT overwhelmed the antioxidant defense mechanism such as the alteration of MT levels in tumor cells.
Oncol Rep 2006 Dec
PMID:Differential up-regulation of metallothionein isoforms in well-differentiated nasopharyngeal cancer cells in vitro by photoactivated hypericin. 1708 67

E. coli has two-component systems composed of histidine kinase proteins and response regulator proteins. For a given extracellular stimulus, a histidine kinase senses the stimulus, autophosphorylates and then passes the phosphates to the cognate response regulators. The histidine kinase in an orthodox two-component system has only one histidine domain where the autophosphorylation occurs, but a histidine kinase in some unusual two-component systems (unorthodox two-component systems) has two histidine domains and one aspartate domain. So, the unorthodox two-component systems have more complex phosphorelay mechanisms than orthodox two-component systems. In general, the two-component systems are required to promptly respond to external stimuli for survival of E. coli. In this respect, the complex multi-step phosphorelay mechanism seems to be disadvantageous, but there are several unorthodox two-component systems in E. coli. In this paper, we investigate the reason why such unorthodox two-component systems are present in E. coli. For this purpose, we have developed simplified mathematical models of both orthodox and unorthodox two-component systems and analyzed their dynamical characteristics through extensive computer simulations. We have finally revealed that the unorthodox two-component systems realize ultrasensitive responses to external stimuli and also more robust responses to noises than the orthodox two-component systems.
Comput Biol Chem 2006 Dec
PMID:The multi-step phosphorelay mechanism of unorthodox two-component systems in E. coli realizes ultrasensitivity to stimuli while maintaining robustness to noises. 1711 85


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