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)

An insertion mutation in the Escherichia coli dsbA gene, coding for periplasmic disulfide oxidoreductase, dramatically reduces the level of OmpF porin protein in the cell envelope. Studies with chromosomal ompF-lacZ operon and gene fusions indicate that this is due to reduced ompF transcription. Identical effects resulted from growth in medium containing the reducing agent dithiothreitol, but the combined effects of the reducing agent and dsbA were no greater than the effects of each individually. The dsbA mutation did not prevent normal regulation of ompF transcription by the local anaesthetic procaine or by osmolarity. OmpF does not contain a cysteine residue, and the sole cysteine residue in the cytoplasmic membrane regulator of ompF transcription, EnvZ, is predicted to be located on the cytoplasmic side of the membrane, and is therefore unlikely to be involved in the effects of the dsbA mutation. The effects of the dsbA mutation and of the reducing agent on ompF transcription may be due to the failure to from an essential disulfide bond in an as yet unidentified envelope protein that affects ompF transcription.
Mol Gen Genet 1993 Mar
PMID:A mutation in the dsbA gene coding for periplasmic disulfide oxidoreductase reduces transcription of the Escherichia coli ompF gene. 848 56

Mouse sperm contain a tyrosine phosphorylated form of hexokinase type 1 (HK1; Kalab et al., 1994: J Biol Chem 269:3810-3817) that has properties consistent with an integral plasma membrane protein. Furthermore, this tyrosine phosphorylated form of HK1 has an extracellular domain and HK1 is localized to both the head and flagellum of nonpermeabilized cells (Visconti et al., 1995c). We have characterized HK1 in mature sperm from sterile tw32/tw5 mice (mutant sperm) that have defects in motility and sperm-egg interaction (Johnson et al., 1995: Dev Biol 168:138-149). Immunoprecipitation of mouse sperm extracts with an antiserum made against purified rat brain HK1 demonstrates the presence of HK1 in mutant sperm. Various biochemical and immunofluorescence assays indicate that at least a portion of the HK1 present in these cells is an integral membrane protein with an extracellular domain located on the sperm head and flagellum. However, immunoblot analysis with anti-phoshotyrosine antibodies demonstrates that HK1 in mutant sperm is not tyrosine phosphorylated. Northern blot and RT-PCR analysis does not indicate any obvious abnormalities in the transcription of somatic or germ cell-specific HK1 isoforms in mutant testes, and RFLP analysis of recombinant mice indicates that no genes specifying HK1 isoforms are located on chromosome 17. We have mapped the locus responsible for the lack of tyrosine phosphorylation of HK1 mutant sperm to the most proximal (to the centromere) of the four inversions within the t haplotype. A male sterility factor is located in this same inversion (Lyon, 1986: Cell 44:357-363). Since the mutant sperm are unable to complete fertilization, there could be a relationship between sterility and the lack of tyrosine phosphorylation of HK1 in these mutant sperm.
Mol Reprod Dev 1996 Jan
PMID:Sperm from mice carrying two t haplotypes do not possess a tyrosine phosphorylated form of hexokinase. 872 Jan 18

In Escherichia coli the histidine kinase sensor protein, EnvZ, undergoes autophosphorylation and subsequently phosphorylates the regulatory protein, OmpR. Modulation of the levels of OmpR-phosphate controls the differential expression of ompF and ompC. While the phosphotransfer reaction between EnvZ and OmpR has been extensively studied, the domains involved in the sensing function of EnvZ are not well understood. We have used a comparative approach to study the sensing function of EnvZ. During our search of numerous bacteria we found that the symbiotic/pathogenic bacterium Xenorhabdus nematophilus contained the operon encoding both ompR and envZ. Nucleotide sequence analysis revealed that EnvZ of X. nematophilus (EnvZX.n.) is composed of 342 amino acid residues, which is 108 residues shorter than EnvZ of E. coli (EnvZE.c.). Amino acid sequence comparison showed that the cytoplasmic domains of the EnvZ molecules shared 57% sequence identity. In contrast, the large hydrophilic periplasmic domain of EnvZE.c. was absent in EnvZX.n., and was replaced by a shorter hydrophobic region. Although the periplasmic domains had diverged extensively, envZX.n. was able to complement a delta envZ strain of E. coli. OmpF and OmpC were differentially produced in response to changes in medium osmolarity in this strain. Further genetic analysis established that heterologous phosphorylation between EnvZX.n. and OmpR of E. coli (OmpRE.c.) accounted for the complementation of the delta envZ strain. In addition we show that the OmpR molecules of X. nematophilus and E. coli share 78% amino acid sequence identity. These results indicate that the EnvZ protein of X. nematophilus was able to sense these changes in the osmolarity of the growth environment and properly regulate the levels of OmpR-phosphate in E. coli.
Mol Microbiol 1995 Aug
PMID:Molecular analysis of the two-component genes, ompR and envZ, in the symbiotic bacterium Xenorhabdus nematophilus. 880 19

In Escherichia coli, levels of the two major outer membrane porin proteins, OmpF and OmpC, are regulated in response to a variety of environmental parameters, and numerous factors have been shown to influence porin synthesis. EnvZ and OmpR control porin-gene transcription in response to osmolarity, and the antisense RNA, MicF, influences ompF translation. In contrast to these characterized factors, some of the components reported to influence porin expression have only modest effects and/or act indirectly. For others, potential regulatory roles, although intriguing, remain elusive. Here we review many of the components that have been reported to influence porin expression, address the potential regulatory nature of these components, and discuss how they may contribute to a regulatory network controlling porin synthesis.
Mol Microbiol 1996 Jun
PMID:From acids to osmZ: multiple factors influence synthesis of the OmpF and OmpC porins in Escherichia coli. 880 44

PhoB is a response-regulator protein from Escherichia coli that controls an adaptive response to limiting phosphate. It is activated by autophosphorylation of a conserved aspartate residue within its regulatory domain. Its primary phospho-donor is its cognate histidine kinase PhoR; however, it also becomes phosphorylated when incubated with acetylphosphate. To further characterize its activation, PhoB was considered to be an acetylphosphatase whose enzymatic mechanism involves a phospho-enzyme intermediate. The kinetic constants for autophosphorylation were determined using 32P-and fluorescence-based assays and indicated that PhoB has a K(m) for acetylphosphate of between 7 and 8 mM. These constants are not consistent with an in vivo role for acetylphosphate in the normal control of the Pho regulon. In addition, when PhoB was phosphorylated by acetylphosphate it eluted from a high-performance liquid chromatography (HPLC) size-exclusion column in two peaks. The larger form of PhoB eluted from the column in a similar manner to a chemically cross-linked dimer of PhoB. The smaller form of PhoB is a monomer. Phosphorylated PhoB bound pho-box DNA approximately 10 times tighter than PhoB. These observations show that PhoB forms a dimer when phosphorylated and suggest that the characteristics of activated PhoB result from its dimerization.
Mol Microbiol 1996 Jun
PMID:The activation of PhoB by acetylphosphate. 880 68

We isolated and characterized three spontaneous mutations leading to trimethylamine N-oxide (TMAO)-independent expression of the tor operon encoding the TMAO-reductase anaerobic respiratory system in Escherichia coli. The mutations lie in a new for regulatory gene, the torS gene, which probably encodes a sensor protein of a two-component regulatory system. One mutation, which leads to full TMAO-constitutive expression, is a 3-amino-acid deletion within the potential N-terminal periplasmic region, suggesting that this region contains the TMAO-detector site. For the other two mutations, a further induction of the tor operon is observed when TMAO is added. Both are single substitutions and affect the linker region located between the detector and the conserved transmitter domains. Thus, as proposed for other sensors, the TorS linker region might play an essential role in propagating conformational changes between the detector and the cytoplasmic signalling regions. The TorS histidine kinase is an unorthodox sensor that contains a receiver and a C-terminal alternative transmitter domain in addition to the domains found in most sensors. Previously, we showed that TMAO induction of the for operon requires the TorR response regulator and the TorT periplasmic protein. Additional genetic data confirm that torS encodes the sensor partner of TorR and TorT. First, insertion within torS abolishes tor operon expression whatever the growth conditions. Second, overexpressed TorR bypasses the requirement for torS, whereas the torT gene product is dispensable for tor operon expression in a torS constitutive mutant. This supports a signal-transduction cascade from TorT to TorR via TorS.
Mol Microbiol 1996 Jun
PMID:An unorthodox sensor protein (TorS) mediates the induction of the tor structural genes in response to trimethylamine N-oxide in Escherichia coli. 880 80

The serine chemoreceptor Tsr and other methyl-accepting chemotaxis proteins (MCPs) control the swimming behaviour of Escherichia coli by generating signals that influence the direction of flagellar rotation. MCPs produce clockwise (CW) signals by stimulating the autophosphorylation activity of CheA, a cytoplasmic histidine kinase, and counter-clockwise signals by inhibiting CheA. CheW couples CheA to chemoreceptor control by promoting formation of MCP/CheW/CheA ternary complexes. To identify MCP structural determinants essential for CheA stimulation, we inserted fragments of the tsr coding region into an inducible expression vector and used a swimming contest called 'pseudotaxis' to select for transformant cells carrying CW-signalling plasmids. The shortest active fragment we found, Tsr (350-470), stimulated CheA in a CheW-dependent manner, as full-length Tsr molecules do. It spans a highly conserved 'core' (370-420) that probably specifies the CheA and CheW contact sites and other determinants needed for stimulatory control of CheA. Tsr (350-470) also carries portions of the left and right arms flanking the core, which probably play roles in regulating MCP signalling state. However, this Tsr fragment lacks all of the methylation sites characteristic of MCP molecules, indicating that methylation segments are not essential for generating receptor output signals.
Mol Microbiol 1996 Feb
PMID:Methylation segments are not required for chemotactic signalling by cytoplasmic fragments of Tsr, the methyl-accepting serine chemoreceptor of Escherichia coli. 882 Jun 44

The ribose-binding protein (RBP) of Escherichia coli, located in the periplasm, binds to ribose and mediates transport and chemotaxis. The regions on the tertiary structure of RBP that interact with the membrane permease, an ABC transporter, were genetically probed by screening a mutation using the chimeric receptor Trz. Trz is a hybrid protein between the periplasmic domain of chemoreceptor Trg and the cytoplasmic portion of osmosensor EnvZ, which provides a system for monitoring the chemotactic interaction of RBP on MacConkey agar plates when coupled with a reporter lacZ fused to an ompC gene. The expression of ompC can be increased by an interaction of ribose-bound RBP with Trz. A transport defect, either in the binding protein or in the membrane permease, causes a signalling-constitutive Lac+ phenotype of Trz even in the absence of ribose. This appears to be due to the presence of a small amount of ribose, which is normally taken up by the high-affinity transport system. By taking advantage of this, we have designed a system for genetic screening that permits a selection for mutations in the binding protein, causing specific defects in permease interaction but not in tactic interaction. Mutant RBPs that were isolated were unable to perform normal ribose uptake and to utilize ribose as a carbon source, while other functions such as taxis and sugar-binding properties were not substantially affected. The mutational changes were repeatedly found in several residues of RBP, concentrating on three surface regions and comprising two domains of the tertiary structure. We suggest that the two regions, including residues 52 and 166, are specifically involved in the permease interaction while the third region, including residues 72, 134, and others, recognizes both the permease and the chemosensory receptor.
Mol Microbiol 1996 Aug
PMID:Genetically probing the regions of ribose-binding protein involved in permease interaction. 887 33

Competence for genetic transformation in certain species of streptococci has been known for many years to be induced by a secreted protease-sensitive pheromone, referred to as the competence factor or activator, which acts as a quorum-sensing signal to co-ordinate expression of late competence genes. We recently reported identification of the pheromone of Streptococcus pneumoniae strain Rx as a small unmodified peptide, which was termed competence-stimulating peptide (CSP). By identifying the gene (comC) encoding the Rx CSP we were able to show that it is synthesized as a precursor peptide containing an N-terminal double-glycine type leader. In the present work, we describe two alleles of the corresponding gene from Streptococcus gordonii strains Challis and NCTC 7865, which are strains with distinct competence pheromones and corresponding specific pheromone reactivities. In addition, the nucleic acid sequences of two genes located downstream of comC were determined; interestingly, these genes encode a two-component signal transduction system. We therefore speculated that their products, a histidine kinase (ComD) and its cognate response regulator (ComE), act downstream of the CSP in competence regulation. By tracing the CSP specificity of the competence response in these strains to strain-specific alleles of comD, we obtained evidence demonstrating that the histidine kinase ComD is the competence-pheromone receptor.
Mol Microbiol 1996 Aug
PMID:Identification of the streptococcal competence-pheromone receptor. 887 47

Three signalling pathways lead to activation of the phosphate (Pho) regulon by phosphorylation of the response-regulator PhoB in Escherichia coli. One pathway responds to the extracellular inorganic phosphate (PI) level and leads to activation by the Pi sensor kinase, PhoR. The other two pathways are Pi independent and are apparent in the absence of PhoR. One Pi-independent pathway responds to the level of an unknown catabolite and leads to activation by the catabolite regulatory sensor kinase, CreC (originally called PhoM); the other Pi-independent pathway responds to acetyl phosphate and leads to activation by a process requiring acetyl phosphate. Here we show that activation of PhoB by acetyl phosphate can require the sensor kinase EnvZ. Accordingly, we propose that the in vivo activation of PhoB by acetyl phosphate (and perhaps other two-component response-regulators as well) probably always requires a certain kinase that can vary depending upon the growth conditions.
Mol Microbiol 1996 Oct
PMID:Involvement of the sensor kinase EnvZ in the in vivo activation of the response-regulator PhoB by acetyl phosphate. 889 16


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