Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: 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)

The CheA histidine kinase initiates the signal transduction pathway of bacterial chemotaxis by autophosphorylating a conserved histidine on its phosphotransferase domain (P1). Site-directed mutations of neighboring conserved P1 residues (Glu-67, Lys-48, and His-64) show that a hydrogen-bonding network controls the reactivity of the phospho-accepting His (His-45) in Thermotoga maritima CheA. In particular, the conservative mutation E67Q dramatically reduces phosphotransfer to P1 without significantly affecting the affinity of P1 for the CheA ATP-binding domain. High resolution crystallographic studies revealed that although all mutants disrupt the hydrogen-bonding network to varying degrees, none affect the conformation of His-45. 15N-NMR chemical shift studies instead showed that Glu-67 functions to stabilize the unfavored N(delta1)H tautomer of His-45, thereby rendering the N(epsilon2) imidazole unprotonated and well positioned for accepting the ATP phosphoryl group.
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PMID:Structural and chemical requirements for histidine phosphorylation by the chemotaxis kinase CheA. 1599 28

Signature-tagged mutagenesis (STM) was used to identify new genes involved in the virulence of the Gram-positive intracellular pathogen Listeria monocytogenes. One of the mutants isolated by this technique had the transposon inserted in virR, a gene encoding a putative response regulator of a two-component system. Deletion of virR severely decreased virulence in mice as well as invasion in cell-culture experiments. Using a transcriptomic approach, we identified 12 genes regulated by VirR, including the dlt-operon, previously reported to be important for L. monocytogenes virulence. However, a strain lacking dltA, was not as impaired in virulence as the DeltavirR strain, suggesting a role in virulence for other members of the vir regulon. Another VirR-regulated gene is homologous to mprF, which encodes a protein that modifies membrane phosphatidyl glycerol with l-lysine and that is involved in resistance to human defensins in Staphylococcus aureus. VirR thus appears to control virulence by a global regulation of surface components modifications. These modifications may affect interactions with host cells, including components of the innate immune system. Surprisingly, although controlling the same set of genes as VirR, the putative cognate histidine kinase of VirR, VirS, encoded by a gene located three genes downstream of virR, was shown not to be essential for virulence. By monitoring the activity of VirR with a GFP reporter construct, we showed that VirR can be activated independently of VirS, for example through a mechanism involving variations in the level of intracellular acetyl phosphate. In silico analysis of the VirR-regulated promoters revealed a VirR DNA-binding consensus site and specific interaction between purified VirR protein and this consensus sequence was demonstrated by gel mobility shift assays. This study identifies a second key virulence regulon in L. monocytogenes, after the prfA regulon.
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PMID:VirR, a response regulator critical for Listeria monocytogenes virulence. 1610 6

We have measured the transcription of several genes that have been implicated as virulence factors in Aspergillus fumigatus, including fos-1, a histidine kinase, two-component signal protein, rhbA, a ras-related protein required for signaling, pksP, a polyketide synthase involved in biosynthesis of melanin, pabA synthetase, an enzyme catalyzing a late step in the biosynthesis of folate, lysF, a homoconitase related to lysine biosynthesis, and cpcA, the transcriptional activator of the cross-pathway control system of amino acid biosynthesis. Transcription levels were determined from in vitro grown organism as well as from lung tissue from mice infected with A. fumigatus. Our data indicate that fos-1 and rhbA transcription increased significantly during the infection in mice, compared to the other genes whose transcription remained the same (pksP, cpcA, pabA) or decreased slightly (lysF). In vitro measurements of transcription compared to transcription in infected lung tissue demonstrated low levels of fos-1 and rhbA, 20-40-fold increases (cpcA, lysF, pabA), while pksP was not detected from cultures. Our data demonstrate that transcription of these genes differs in vitro versus during disease.
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PMID:Expression of Aspergillus fumigatus virulence-related genes detected in vitro and in vivo with competitive RT-PCR. 1620 68

Using a yeast two-hybrid assay system, it was demonstrated that the four-helix bundle of the Rhodobacter sphaeroides PrrB histidine kinase both serves as the interaction site for the regulatory domain of its cognate response regulator PrrA and is the primary determinant of the interaction specificity. The alpha-helix 1 and its flanking turn region within the dimerization domain (DD) of the PrrB histidine kinase appear to play an important role in conferring the recognition specificity for the PrrA response regulator on the DD. The catalytic ATP-binding domain of the histidine kinase, which functions as the catalytic unit for the phosphotransfer reaction from ATP to the conserved histidine residue in the DD, also appears to contribute to the enhancement of the recognition specificity conferred by the DD. It was also revealed that replacement of Asp-63 and Lys-113 of the PrrA response regulator by alanine abolished protein-protein interactions between PrrA and its cognate histidine kinase PrrB, whereas mutations of Asp-19, Asp-20 and Thr-87 to alanine did not affect protein-protein interactions, indicating that among the active site residues of PrrA, Asp-63 and Lys-113 are important not only in the function of PrrA but also for protein-protein interactions between PrrA and PrrB.
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PMID:Interacting specificity of a histidine kinase and its cognate response regulator: the PrrBA system of Rhodobacter sphaeroides. 1684 10

Phytochromes are widely distributed photochromic biliprotein photoreceptors. Typical bacterial phytochromes such as Agrobacterium Agp1 have a C-terminal histidine kinase module; the N-terminal chromophore module induces conformational changes in the protein that lead to modulation of kinase activity. We show by protein cross-linking that the C-terminal histidine kinase module of Agp1 mediates stable dimerization. The fragment Agp1-M15, which comprises the chromophore module but lacks the histidine kinase module, can also form dimers. In this fragment, dimer formation was stronger for the far-red-absorbing form Pfr than for the red-absorbing form Pr. The same or similar behavior was found for Agp1-M15Delta9N and Agp1-M15Delta18N, which lack 9 and 18 amino acids of the N-terminus, respectively. The fragment Agp1-M20, which is derived from Agp1-M15 by truncation of the C-terminal "PHY domain" (191 amino acids), can also form dimers, but dimerization is independent of irradiation conditions. The cross-linking data also showed that the PHY domain is in tight contact with Lys 16 of the protein and that the nine N-terminal amino acids mediate oligomer formation. Limited proteolysis shows that the hinge region between the chromophore module and the histidine kinase and a part of the PHY domain become exposed upon Pr to Pfr photoconversion.
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PMID:Protein conformational changes of Agrobacterium phytochrome Agp1 during chromophore assembly and photoconversion. 1733 89

In bacterial pathogenesis, virulence gene regulation is controlled by two-component regulatory systems. In Escherichia coli, the EnvZ/OmpR two-component system is best understood as regulating expression of outer membrane proteins, but in Salmonella enterica, OmpR activates transcription of the SsrA/B two-component system located on Salmonella pathogenicity island 2 (SPI-2). The response regulator SsrB controls expression of a type III secretory system in which effectors modify the vacuolar membrane and prevent its degradation via the endocytic pathway. Vacuolar modification enables Salmonella to survive and replicate in the macrophage phagosome and disseminate to the liver and spleen to cause systemic infection. The signals that activate EnvZ and SsrA are unknown but are related to the acidic pH encountered in the vacuole. Our previous work established that SsrB binds to regions of DNA that are AT-rich, with poor sequence conservation. Although SsrB is a major virulence regulator in Salmonella, very little is known regarding how it binds DNA and activates transcription. In the present work, we solved the structure of the C-terminal DNA binding domain of SsrB (SsrB(C)) by NMR and analyzed the effect of amino acid substitutions on function. We identified residues in the DNA recognition helix (Lys(179), Met(186)) and the dimerization interface (Val(197), Leu(201)) that are important for SsrB transcriptional activation and DNA binding. An essential cysteine residue in the N-terminal receiver domain was also identified (Cys(45)), and the effect of Cys(203) on dimerization was evaluated. Our results suggest that although disulfide bond formation is not required for dimerization, dimerization occurs upon DNA binding and is required for subsequent activation of transcription. Disruption of the dimer interface by a C203E substitution reduces SsrB activity. Modification of Cys(203) or Cys(45) may be an important mode of SsrB inactivation inside the host.
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PMID:Structural and functional analysis of the C-terminal DNA binding domain of the Salmonella typhimurium SPI-2 response regulator SsrB. 1912 46

Daptomycin is a lipopeptide antibiotic used clinically to treat infections caused by Gram-positive bacteria. Laboratory studies have shown that Staphylococcus aureus resistance to daptomycin occurs stepwise and slowly. Mutations associated with decreased susceptibility were mapped in mprF, yycG, rpoB, and rpoC, each giving about twofold increases in the minimal inhibitory concentration (MIC) and combinations giving higher MICs. The mprF gene encodes a dual functional enzyme that couples lysine to phosphatidylglycerol (PG) and transfers the lysyl-PG (LPG) to the outer leaflet of the membrane. LPG is less acidic than PG, and thus reduces the binding of Ca(++)-bound daptomycin to bacterial membranes. The mprF mutants have higher LPG/PG ratios in the membrane outer leaflet and bind less daptomycin than the wild-type strain. YycG is a sensor histidine kinase of a two component signal transduction system required for viability in many low G+C Gram-positive bacteria. The observation of DapR mutations in yycG suggests that YycG may be a target for daptomycin antibacterial activity. Daptomycin inserts into PG rich membrane at the cell division septum, but also inserts into lung surfactant, explaining why it failed to meet non-inferiority criteria in clinical trials for community acquired pneumonia (CAP). Recent advances in biosynthetic engineering have provided new tools to generate novel lipopeptides with modifications in the core peptide: several were very potent antibiotics against Gram-positive pathogens, and some were active in the presence of surfactant.
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PMID:Daptomycin: mechanisms of action and resistance, and biosynthetic engineering. 1930 6

The Gram-positive soil bacterium Corynebacterium glutamicum is used in microbial biotechnology for the large-scale production of amino acids, e.g., L: -glutamate and L: -lysine. We have studied the response of this organism to hyperosmotic challenge at the level of both transcription and protein activity. Two systems responding to hyperosmotic stress in C. glutamicum are reviewed here, the two component system MtrAB and the glycine-betaine uptake system BetP. The osmosensory two-component system consists of the membrane-bound histidine kinase MtrB and the soluble response regulator MtrA. MtrB was shown to perceive a so far unknown physical stimulus related to hyperosmotic stress via the cytoplasmically oriented phosphorylation domain, and to transduce the signal to the DNA via MtrA. The secondary active transporter BetP takes up betaine in cotransport with two Na(+) ions. BetP responds to hyperosmotic stress by increased transcription mediated via MtrAB signaling, and by instant activation of transport. In the mechanism of BetP activation, the C-terminal, regulatory domain of BetP, the cytoplasmic concentration of K(+), and negative membrane surface charges are involved. The molecular mechanism of the activation process is discussed in relation to the recently published X-ray structure of BetP.
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PMID:Osmosensing and osmosignaling in Corynebacterium glutamicum. 1930 62

Some Gram-negative bacteria express a novel enzyme with lysine-epsilon-oxidase (LOD) activity (EC 1.4.3.20). The oxidation of l-Lys generates, among other products, hydrogen peroxide, which confers antimicrobial properties to this kind of enzyme and has been shown to be involved in cell death during biofilm development and differentiation. In addition to LOD, the melanogenic marine bacterium Marinomonas mediterranea, which forms part of the microbiota of the marine plant Posidonia oceanica, expresses two other oxidases of biotechnological interest, a multicopper oxidase, PpoA, with laccase activity and a tyrosinase named PpoB, which is responsible for melanin synthesis. By using both lacZ fusions with the lodAB promoter and quantitative reverse transcription-PCR (qRT-PCR), this study shows that the hybrid sensor histidine kinase PpoS regulates LOD activity at the transcriptional level. Although PpoS also regulates PpoA and PpoB, in this case, the regulatory effect cannot be attributed only to a transcriptional regulation. Further studies indicate that LOD activity is induced at the posttranscriptional level by l-Lys as well as by two structurally similar compounds, l-Arg and meso-2,6-diaminopimelic acid (DAP), neither of which is a substrate of the enzyme. The inducing effect of these compounds is specific for LOD activity since PpoA and PpoB are not affected by them. This study offers, for the first time, insights into the mechanisms regulating the synthesis of the antimicrobial protein lysine-epsilon-oxidase in M. mediterranea, which could be important in the microbial colonization of the seagrass P. oceanica.
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PMID:Regulation of the Marinomonas mediterranea antimicrobial protein lysine oxidase by L-lysine and the sensor histidine kinase PpoS. 2065 78

The CsrRS (or CovRS) two component system controls expression of up to 15% of the genome of group A Streptococcus (GAS). While some studies have suggested that the sensor histidine kinase CsrS responds to membrane perturbations as a result of various environmental stresses, other data have implicated the human antimicrobial peptide LL-37 and extracellular Mg(2+) as specific signals. We now report that Mg(2+) and LL-37 have opposite effects on expression of multiple genes that are activated or repressed by the transcriptional regulator CsrR. Using a GAS isolate representative of the recently emerged and widely disseminated M1T1 clone implicated in severe invasive disease, we found marked up-regulation by CsrRS of multiple virulence factors including pyrogenic exotoxin A, DNase Sda1, streptolysin O, and the hyaluronic acid capsular polysaccharide, among others. Topology and surface protein labeling studies indicated that CsrS is associated with the bacterial cell membrane and has a surface-exposed extracellular domain accessible to environmental ligands. Replacement of a cluster of three acidic amino acids with uncharged residues in the extracellular domain of CsrS abrogated LL-37 signaling and conferred a hyporesponsive phenotype consistent with tonic activation of CsrS autokinase activity, an effect that could be overridden by mutation of the CsrS active site histidine. Both loss- and gain-of-function mutations of a conserved site in the receiver domain of CsrR established an essential role for lysine 102 in CsrS-to-CsrR signal transduction. These results provide strong evidence that Mg(2+) and LL-37 are specific signals that function by altering CsrS autokinase activity and downstream phosphotransfer to CsrR to modulate its activity as a transcriptional regulator. The representation of multiple antiphagocytic and cytotoxic factors in the CsrRS regulon together with results of in vitro phagocytic killing assays support the hypothesis that CsrRS mediates conversion of GAS from a colonizing to an invasive phenotype in response to signaling by host LL-37.
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PMID:Signal transduction through CsrRS confers an invasive phenotype in group A Streptococcus. 2204 38


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