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)

Taz1-1 is Tar-EnvZ chimeric receptor that is able to induce ompC-lacZ expression in response to aspartate. Previous studies indicated that aspartate binding to the receptor domain of the Taz1-1 receptor modulated the ratio of kinase and phosphatase activities of the cytoplasmic signaling domain. The 80-residue segment of chemoreceptors that is located between the second transmembrane domain and the signaling domain was defined as the linker region. The Taz1-1 chimeric receptor contains 43 amino acid residues of the Tar linker region. In order to understand further the function of the linker region in transmembrane signaling, site-directed random mutagenesis was carried out on the conserved Ala231 in the linker region. Substitution mutations with Val, Glu, Gly, Thr, Lys and His gave the locked "off-mode" form (low ompC-lacZ expression), and substitution mutations with Ile and Leu resulted in the locked "on-mode" form (constitutive ompC-lacZ expression). All the mutant Taz1-1 receptors still retained both OmpR kinase and phospho-OmpR phosphatase activities. Interestingly Taz1N6, a kinase defective mutant, was able to complement with Taz1H1, a phosphatase defective mutant, carrying an off-mode mutant at position 231 to restore Asp-inducible ompC-lacZ expression, but not with Taz1H1 carrying an on-mode mutation. These results suggest that the residue at position 231 in Taz1-1 plays a key role in signal transduction.
J Mol Biol 1994 Dec 16
PMID:Transmembrane signaling. Mutational analysis of the cytoplasmic linker region of Taz1-1, a Tar-EnvZ chimeric receptor in Escherichia coli. 799 Jan 35

The Escherichia coli regulatory proteins, EnvZ and OmpR, are crucially involved in expression of the outer membrane proteins OmpF/OmpC in response to the medium osmolarity. The EnvZ protein is presumably a membrane-located osmotic sensor (or signal transducer), which exhibits both kinase and phosphatase activities specific for the OmpR protein. To examine the functional importance of the membrane-spanning segments (named TM1 and TM2) of EnvZ molecules in transmembrane signalling, a set of EnvZ mutants, each having amino acid substitutions within the membrane-spanning regions, was characterized in terms of both their in vivo phenotype and in vitro catalytic activities. One of them, characterized further, has an amino acid change (Pro-41 to Ser or Leu) in TM1, and appeared to be defective in its phosphatase activity but not in its kinase activity. This EnvZ mutant conferred a phenotype of OmpF-/OmpC-constitutive. For this EnvZ(P41S or P41L) mutant, a set of intragenic suppressors, each exhibiting a wild-type phenotype of OmpF+/OmpC+, was isolated. These suppressor mutants were revealed to have an additional amino acid change within either TM1 or TM2. Furthermore, they exhibited restored phosphatase activity (i.e., both kinase+ and phosphatase+ activities). It was further demonstrated that one of the suppressors, EnvZ(Arg-180 to Trp in TM2), was able to suppress the defects in both the in vivo phenotype and the in vitro catalytic activities caused by EnvZ(P41S), through intermolecular complementation. These results are best interpreted as meaning that an intimate intermolecular interaction between the membrane-spanning segments of EnvZ is crucial for transmembrane signalling per se in response to an external osmotic stimulus.
Mol Microbiol 1994 Aug
PMID:Transmembrane signal transduction by the Escherichia coli osmotic sensor, EnvZ: intermolecular complementation of transmembrane signalling. 799 60

Penicillin resistance in Streptococcus pneumoniae has been attributed so far to the production of penicillin-binding protein (PBP) variants with decreased affinities for beta-lactam antibiotics. Cefotaxime-resistant laboratory mutants, selected after several steps on increasing concentrations of this beta-lactam, become deficient in transformation as well. A DNA fragment conferring both cefotaxime resistance and transformation deficiency was isolated and cloned from the mutant C306. The cefotaxime resistance associated with this resistance determinant was not accompanied with apparent changes in PBP properties, and it mapped on the chromosome distinct from the known resistance determinants, genes encoding PBP2x, PBP1a or PBP2b. Determination of a 2265 bp DNA sequence of the resistance determinant revealed two open reading frames, ciaR and ciaH, whose deduced amino acid sequence identified the corresponding proteins as the response regulator and histidine kinase receptor, respectively (members of the two families of bacterial signal-transducing proteins). Two hydrophobic peptide regions divided the histidine kinase CiaH into two putative domains: an N-terminal extracellular sensor part, and an intracellular C-terminal domain with the conserved His-226 residue, the presumed phosphorylation site. The single point mutations responsible for cefotaxime-resistance and transformation deficiency of C306 and of another two independently isolated cefotaxime-resistant mutants were each located in the C-terminal half of CiaH. A small extracellular protein, the competence factor, is required for induction of competence. Neither C306 nor the transformants obtained with the mutated ciaH gene produced competence factor, and exogenous competence factor could not complement the transformation deficiency, indicating that the signal-transducing system cia is involved in early steps of competence regulation.
Mol Microbiol 1994 May
PMID:A two-component signal-transducing system is involved in competence and penicillin susceptibility in laboratory mutants of Streptococcus pneumoniae. 806 67

The wilt-inducing phytopathogen Pseudomonas solanacearum produces several extracellular virulence factors, both polysaccharides (EPS I) and proteins (EXPs), which are independently regulated by a LysR-type transcriptional regulator, PhcA, and a histidine kinase sensor, VsrB. Here we characterize a third locus, vsrA, which is also required for normal production of EPS I, some EXPs and wilt disease. Analysis of eps::lacZ reporters in vsrA mutants showed that, like vsrB and phcA, vsrA is required for maximal expression (transcription) of eps, which contains some of the genes necessary for production of EPS I. Unlike vsrB and phcA mutants, however, eps transcription (and EPS I production) by vsrA mutants varies from 3 to 17% of wild-type levels, depending on growth conditions. Inactivation of vsrA also causes a dramatic reduction in production of three species of EXPs (28 kDa, 48 kDa, and 66 kDa), and an apparent increase in production of a few other EXPs. Unlike most other EPS-deficient P. solanacearum strains, vsrA mutants caused almost no disease symptoms when 10(4) cells were stem-inoculated into tomato plants. This correlated with a greater than 10-fold reduction in their ability to grow in planta. vsrA was cloned from a P. solanacearum genomic library by complementation of the vsrA mutant and was further subcloned on a 2.3 kb DNA fragment. PhoA fusion analysis and subcellular localization of the vsrA gene product in Escherichia coli maxicells suggest that it is a 53 kDa membrane-associated protein. Analysis of the nucleotide sequence of vsrA revealed a 502 residue open reading frame with homology to the histidine kinase domain of sensors in the two-component regulator family. This discovery shows that EPS I production by P. solanacearum is simultaneously controlled by dual two-component sensors.
Mol Microbiol 1994 Feb
PMID:VsrA, a second two-component sensor regulating virulence genes of Pseudomonas solanacearum. 815 73

To assess the requirements for papilloma formation in transgenic mice that overexpress transforming growth factor-alpha (TGF-alpha) in the epidermis (HK1.TGF alpha), we tested the sensitivity of HK1.TGF alpha mice to tumor promotion with 12-O-tetradecanoylphorbol-13-acetate (TPA) and analyzed the resultant papillomas for synergic c-Ha-ras activation and overexpression. We observed that HK1.TGF alpha mice were highly sensitive to TPA promotion, exhibiting multiple papillomas as early as the third week of treatment. After 60 wk of promotion, malignant conversion was not observed and tumors regressed upon removal of the TPA promotion stimulus. Most of the TPA-induced papillomas did not have detectable c-Ha-ras mutations at codons 12, 13, or 61, but three papillomas arising after long-term TPA promotion (5-7 mo) exhibited c-Ha-ras activation at codon 61 (A-->T and A-->G). Conversely, spontaneous papillomas arising without TPA promotion, including persisting autonomous papillomas, were all negative for activating c-Ha-ras mutations. Both spontaneous and TPA-induced HK1.TGF alpha papillomas expressed c-Ha-ras message levels similar to those in normal, nontransgenic epidermis or HK1.TGF alpha hyperplastic epidermis. These data demonstrate that TGF-alpha overexpression can be an initiating event for TPA promotion, that papillomatogenesis in HK1.TGF alpha mice proceeds frequently via a pathway independent of Ha-ras activation or overexpression, and, thus, that other events are required for autonomous growth and malignant conversion.
Mol Carcinog 1994 May
PMID:Epidermal expression of transforming growth factor-alpha in transgenic mice: induction of spontaneous and 12-O-tetradecanoylphorbol-13-acetate-induced papillomas via a mechanism independent of Ha-ras activation or overexpression. 818 25

Taz1 is a hybrid receptor in the Escherichia coli cytoplasmic membrane, consisting of the N-terminal ligand binding domain of Tar (a chemoreceptor for aspartate) and the C-terminal signaling domain of EnvZ (an osmosensor). The binding of aspartate to an extra cytoplasmic domain induces the transmembrane signal to the cytoplasmic signaling domain. The signaling domain functioning as a protein kinase evokes a response by transferring a phosphate from an intracellular histidine to OmpR. This domain also encodes an OmpR-specific phosphatase whose action is crucial in completing the OmpR phosphorylation cycle. Phosphorylated OmpR acts as a transcriptional activator for the ompC gene. A number of mutations were introduced into the signaling domain in conserved sequences of the prokaryotic histidine kinase family. All Taz1 mutants lost the ability to both autophosphorylate the histidine residue and transfer the phosphate to OmpR. These mutated receptors were unable to activate ompC-lacZ expression. However, ompC-lacZ was able to be activated by complementation of Taz1 mutants. In some combinations, two different defective Taz1 mutants could restore both OmpR kinase and phosphatase activities when co-expressed. In other combinations only kinase activity was restored. Aspartate-inducible ompC-lacZ expression was restored only in the former cases, while in the latter cases ompC-lacZ expression became constitutive. These results indicate that the kinase activity is essential to activate ompC expression while the phosphatase activity is required to regulate ompC gene expression in a ligand-dependent manner.
J Mol Biol 1993 May 20
PMID:Requirement of both kinase and phosphatase activities of an Escherichia coli receptor (Taz1) for ligand-dependent signal transduction. 838 84

Taz1 is a hybrid receptor, in which the periplasmic receptor domain of Tar, an aspartate chemoreceptor, is fused with the cytoplasmic signaling domain of EnvZ, an osmosensor. Taz1 is able to induce ompC-lacZ expression in response to aspartate added to the medium. We introduced amino acid substitution mutations in the highly conserved region of the signaling domain of Tar near the Tar-EnvZ junction. The same mutations in Tsr, a serine chemoreceptor, are known to lock the flagella rotation in either a clockwise (CW) or in a counter-clockwise (CCW) mode. It was found that a CW-biased mutation in Taz1 resulted in ompC-lacZ expression in the "off mode", or low ompC-lacZ expression in both the absence and presence of aspartate, while CCW-biased mutations caused ompC-lacZ expression in the "on mode", or constitutive expression regardless of aspartate. The OmpR kinase and phospho-OmpR phosphatase activities of the wild-type and mutant Taz proteins were also examined in response to aspartate. The phosphatase activity of the wild-type Taz1 was found to decrease in the presence of aspartate, while the OmpR kinase activity remained constant. This indicated that aspartate binding to the Taz1 receptor domain modulates the ratio of kinase to phosphatase activity of the signaling domain. An increased kinase to phosphatase ratio in the presence of aspartate resulted in higher levels of phospho-OmpR in the cell and therefore induced ompC-lacZ expression. In contrast to the wild-type Taz1 protein, the enzymatic activities of CW as well as CCW mutants did not change in response to aspartate, indicating that mutant Taz proteins are incapable of transducing the signal across the membrane as a result of a locked conformation of the signaling domain in either the on or off mode.
J Mol Biol 1993 Jul 20
PMID:Ligand binding to the receptor domain regulates the ratio of kinase to phosphatase activities of the signaling domain of the hybrid Escherichia coli transmembrane receptor, Taz1. 839 37

Two ligand (aspartate)-binding pockets are formed at the interface between the subunits of the Tar homodimer, a bacterial chemoreceptor. Using mutant heterodimers of a hybrid receptor, Taz1, which consists of the external domain of Tar and the cytoplasmic domain of EnvZ, we disrupted either one or the other of the two ligand-binding pockets. We found that occupation of only one of the ligand-binding pockets was sufficient for induction of a transmembrane signal, and that the subunit responsible for the binding of the amino group of the ligand transduces the signal.
J Mol Biol 1993 Jul 20
PMID:Ligand binding induces an asymmetrical transmembrane signal through a receptor dimer. 839 38

The fadL gene of Escherichia coli codes for an outer membrane protein that is involved in the uptake of long-chain fatty acids. Uptake is regulated by environmental osmolarity, and decreases when the cells are grown under conditions of high osmolarity. A temperature-sensitive mutant that requires fatty acid for growth at 42 degrees C was unable to grow at the high temperature even in the presence of fatty acid if the medium contained 10% sucrose. Promoter activity of the fadL gene in vivo was repressed by high osmolarity in a FadR repressor null mutant. Furthermore, in vitro transcription of the fadL gene was strongly repressed by the addition of OmpR and EnvZ proteins. The results of gel retardation and DNase I protection experiments indicated that OmpR, after incubation with the protein kinase EnvZ, specifically binds to at least four sites around the fadL promoter, two upstream and two downstream from the transcriptional start site. These results suggest that transcription of the fadL gene is osmotically regulated by the OmpR-EnvZ two-component system.
Mol Gen Genet 1993 Sep
PMID:Osmoregulation of the fatty acid receptor gene fadL in Escherichia coli. 841 82

A DNA fragment was cloned from Bacteroides fragilis that bestowed low-level tetracycline resistance to Escherichia coli strains harbouring the cloned fragment on a multicopy plasmid. The tetracycline resistance determinant was localized to a 4.3kb Bg/II-PstI subfragment of the original clone. DNA sequence analysis of this fragment revealed that it contained an operon encoding two proteins: one of 519 amino acids, RprX, and a second of 236 amino acids, RprY. Protein sequence analysis revealed that the two proteins shared sequence identity with a family of multicomponent signal-transducing regulatory proteins identified from many diverse bacterial genera. RprX shared identity with the first component of the regulatory system, the histidine protein kinase receptor (for example EnvZ, PhoR, CheA, and VirA). RprY shared identity with the second member of the regulatory protein pair, the regulatory response protein (for example OmpR, PhoB, CheY, and VirG). Expression of these proteins from a multicopy plasmid vector in E. coli resulted in a decrease in the level of the outer membrane porin protein OmpF and an increase in the level of the outer membrane porin protein OmpC. The decrease in OmpF levels correlates with, and may be the cause of, the increased tetracycline resistance. Regulation of the levels of OmpF and OmpC is normally controlled by a multicomponent signal-transducing regulatory pair of proteins, EnvZ and OmpR. The effect RprX and RprY have on OmpF expression is mediated at the level of transcription. Thus, RprX and RprY may be interfering with the normal regulation of OmpF by OmpR and EnvZ.
Mol Microbiol 1993 Mar
PMID:Cloning and identification of a two-component signal-transducing regulatory system from Bacteroides fragilis. 846 17


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