Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In response to nitrate availability, Escherichia coli regulates the synthesis of a number of enzymes involved in anaerobic respiration and fermentation. When nitrate is present, nitrate reductase (narGHJI) gene expression is induced, while expression of the DMSO/TMAO reductase (dmsABC), fumarate reductase (frdABCD) and fermentation related genes are repressed. The narL and narX gene products are required for this nitrate-dependent control, and apparently function as members of a two-component regulatory system. NarX is a presumed sensor-transmitter for nitrate and possibly molybdenum detection. The presumed response-regulator, NarL, when activated by NarX then binds at the regulatory DNA sites of genes to modulate their expression. In this study a third nitrate regulatory gene, narQ, was identified that also participates in nitrate-dependent gene regulation. Strains defective in either narQ or narX alone exhibited no nitrate-dependent phenotype whereas mutants defective in both narQ and narX were fully inactive for nitrate-dependent repression or activation. In all conditions tested, this regulation required a functional narL gene product. These findings suggest that the narX and narQ products have complementary sensor-transmitter functions for nitrate detection, and can work independently to activate NarL, for eliciting nitrate-dependent regulation of anaerobic electron transport and fermentation functions. The narQ gene was cloned, sequenced, and compared with the narX gene. Both gene products are similar in size, hydrophobicity, and sequence, and contain a highly conserved histidine residue common to sensor-transmitter proteins.
Mol Microbiol 1992 Jul
PMID:Identification and characterization of narQ, a second nitrate sensor for nitrate-dependent gene regulation in Escherichia coli. 150 40

The apo-nitrate reductase precursor in an Escherichia coli chlB mutant preparation obtained following growth in the presence of tungstate is activated by incubation with protein FA and a heat-treated preparation from an E. coli crude extract. We show that the requirement for heat-treated E. coli crude extract can be fulfilled by material obtained from either of two heat-denatured purified E. coli molybdoenzymes, namely nitrate reductase or trimethylamine N-oxide reductase. Apo-trimethylamine N-oxide reductase precursor in the tungstate-grown chlB preparation can be activated in a similar manner with material from either heat-denatured molybdoenzyme. The active component in the denatured molybdoenzyme preparations is shown to be the molybdenum cofactor by Neurospora crassa nit1 molybdenum cofactor assay, size estimation and fluorimetric analysis. The direct demonstration of the requirement for molybdenum cofactor in the E. coli tungstate-grown chlB complementation system is an important step towards the molecular definition of the activation process and an understanding of the mechanism of cofactor acquisition during molybdoenzyme biosynthesis.
Mol Microbiol 1990 Apr
PMID:Molybdenum cofactor requirement for in vitro activation of apo-molybdoenzymes of Escherichia coli. 214 Oct 97

A mutant of Escherichia coli K-12, JCB606, which lacks all five c-type cytochromes synthesized during anaerobic growth in the presence of nitrite or trimethylamine-N-oxide (TMAO), was totally defective in Nrf activity and also partially defective in TMAO reductase activity. The mutation in strain JCB606 was shown to affect expression of the tor operon, which contributes almost equally with the products of the dms operon to the rate of TMAO reduction by bacteria during anaerobic growth in the presence of TMAO. The mutation in strain JCB606, dipZ, was mapped by P1 transduction close to the mel operon at co-ordinate 4425 on the E. coli chromosome, the gene order being nrf-fdhF-mel-dipZ-ampC. Recombinant plasmids that restored Nrf activity to test-tube cultures of the mutant were isolated from a cosmid library. A 2.7 kb EcoRV-SmaI fragment (co-ordinates 4443 to 4446 kb on the physical map of the E. coli chromosome) was found potentially to encode three genes arranged in at least two operons. The second gene, dipZ, was sufficient to complement the JCB606 mutation. The translated DNA sequence predicts that DipZ is a 53 kDa integral membrane protein with a 37 kDa N-terminal domain including at least six membrane-spanning helices and a 16 kDa carboxy-terminal hydrophilic domain which includes a protein disulphide isomerase-like motif. It is suggested that DipZ is essential for maintaining cytochrome c apoproteins in the correct conformations for the covalent attachment of haem groups to the appropriate pairs of cysteine residues.
Mol Microbiol 1995 Mar
PMID:The biogenesis of c-type cytochromes in Escherichia coli requires a membrane-bound protein, DipZ, with a protein disulphide isomerase-like domain. 762 67

The trimethylamine N-oxide (TMAO) respiratory system is subject to a strict positive control by the substrate. This property was exploited in the performance of miniMu replicon-mediated in vivo cloning of the promoter region of gene(s) positively regulated by TMAO. This region, located at 22 min on the chromosome, was shown to control the expression of a transcription unit composed of three open reading frames, designated torC, torA and torD, respectively. The presence of five putative c-type haem-binding sites within the TorC sequence, as well as the specific biochemical characterization, indicated that torC encodes a 43,300 Da c-type cytochrome. The second open reading frame, torA, was identified as the structural gene for TMAO reductase. A comparison of the predicted amino-terminal sequence of the torA gene product to that of the purified TMAO reductase indicated cleavage of a 39 amino acid signal peptide, which is in agreement with the periplasmic location of the enzyme. The predicted TorA protein contains the five molybdenum cofactor-binding motifs found in other molybdoproteins and displays extensive sequence homology with BisC and DmsA proteins. As expected, insertions in torA led to the loss of TMAO reductase. The 22,500 Da polypeptides encoded by the third open reading frame does not share any similarity with proteins listed in data banks.
Mol Microbiol 1994 Mar
PMID:TMAO anaerobic respiration in Escherichia coli: involvement of the tor operon. 802 86

Vitamin A and other fat-soluble hormones and vitamins have important roles as modulators of essential biological processes such as homeostasis, development, differentiation, and oncogenesis and also as regulators of the immune system. The active form of vitamin A, retinoic acid, as well as vitamin D3 and thyroid hormones exert their actions by binding to specific nuclear receptors that represent one subfamily of the steroid/thyroid hormone receptor superfamily. To identify new members of the retinoid/thyroid hormone receptor subfamily that could play a role in the immune system, a screening of a T cell cDNA library was performed using a retinoid X receptor probe. A clone was isolated encoding a novel nuclear receptor expressed mainly in the thymus and T cell lines. This new receptor, TOR (thymus orphan receptor), is most closely related in both its DNA-binding domain and ligand-binding domain, 90% and 53%, respectively, to ROR alpha/RZR alpha and clusters with these two receptors and RZR beta in a phylogenetic tree, when both the DNA-binding domain and the ligand-binding domain sequences of nuclear receptors are compared. Thus, TOR is part of a subgroup of receptors, one of which has recently been reported to be activated by melatonin. TOR binds specifically to a direct repeat of the half-site sequence 5'-AGGTCA-3' with a four- or five-nucleotide spacer, DNA sequences that also serve as binding sites for thyroid hormone (TR), and retinoic acid receptors (RAR). In transient transfection experiments TOR does not activate a reporter gene carrying these sequences in the absence or the presence of any known nuclear receptor ligands. TOR, however, is able to repress TR and RAR activity on DR-4-TREs or DR-5-RAREs, respectively. Therefore, our data suggest that TOR, similar to COUP-TF, can negatively regulate retinoic acid and thyroid hormone signals. However, the response elements recognized by TOR and COUP-TF differ as do the expression patterns of these receptors. Thus, one important role of TOR could be to modulate retinoid and thyroid hormone signals in the thymus.
Mol Endocrinol 1995 Dec
PMID:TOR: a new orphan receptor expressed in the thymus that can modulate retinoid and thyroid hormone signals. 861 4

Saccharomyces cerevisiae cells treated with the immunosuppressant rapamycin or depleted for the targets of rapamycin TOR1 and TOR2 arrest growth in the early G1 phase of the cell cycle. Loss of TOR function also causes an early inhibition of translation initiation and induces several other physiological changes characteristic of starved cells entering stationary phase (G0). A G1 cyclin mRNA whose translational control is altered by substitution of the UBI4 5' leader region (UBI4 is normally translated under starvation conditions) suppresses the rapamycin-induced G1 arrest and confers starvation sensitivity. These results suggest that the block in translation initiation is a direct consequence of loss of TOR function and the cause of the G1 arrest. We propose that the TORs, two related phosphatidylinositol kinase homologues, are part of a novel signaling pathway that activates eIF-4E-dependent protein synthesis and, thereby, G1 progression in response to nutrient availability. Such a pathway may constitute a checkpoint that prevents early G1 progression and growth in the absence of nutrients.
Mol Biol Cell 1996 Jan
PMID:TOR controls translation initiation and early G1 progression in yeast. 2289 Oct 31

The operon encoding the periplasmic enzymes dimethyl sulfoxide reductase (DMSOR) and trimethylamine N-oxide reductase (TMAOR) from the purple, non-sulfur, photosynthetic bacterium Rhodobacter capsulatus was isolated, cloned and sequenced, and its chromosomal location determined. It was shown by analytical and crystallographic data that DMSOR and TMAOR are identical enzymes. Degenerate primers were derived from short peptide sequences generated by automated Edman degradation and a 700 bp fragment was amplified by nested PCR, subsequently cloned and radioactively labeled to screen a prepared lambda DASH library. Positive lambda clones were subcloned into pBluescript and subsequently transformed into Escherichia coli to sequence the DMSOR/ TMAOR operon. The promoter consisted of an A + T-rich region followed by a -35 region, a putative ribosome binding site, and a leader sequence of 13 amino acid residues. The transcription terminator was a G + C-rich dyad sequence capable of forming a hairpin structure, which may act rho-independently. An optimized protein purification of the wild-type enzyme is also described, giving high yields (5 mg protein per liter of culture) and a specific activity of 30 units/mg. The molecular mass was determined by electrospray mass spectrometry to be 85,034 Da; from the deduced amino acid sequence the molecular mass of the apoenzyme was 85,033 Da.
J Mol Biol 1996 Oct 18
PMID:Isolation, cloning, sequence analysis and localization of the operon encoding dimethyl sulfoxide/trimethylamine N-oxide reductase from Rhodobacter capsulatus. 889 Sep 11

Two-component regulatory systems allow cells to adapt to environmental changes. In Escherichia coli, the TorS/TorR two-component system induces the expression of the tor structural operon encoding the trimethylamine N-oxide reductase respiratory system in response to substrate availability. TorS belongs to a sensor subfamily that includes a classical transmitter domain, a receiver, and a C-terminal alternative transmitter domain. The histidine phosphorylation sites of each TorS transmitter domain and the aspartate phosphorylation site of the TorS receiver were individually changed by site-directed mutagenesis. All three phosphorylation sites proved essential for in vivo induction of the tor structural operon and for in vitro transphosphorylation of the cognate TorR response regulator. The His to Gln change in the classical transmitter domain abolished TorS autophosphorylation, whereas TorS underwent significant autophosphorylation when the phosphorylation site of its receiver or alternative transmitter was changed. Complementation between pairs of defective TorS proteins was achieved in vitro, allowing TorR transphosphorylation. This strongly suggests that TorS is a multimer in which intermolecular phosphorylation occurs. The wild-type alternative transmitter domain alone was shown to complement a TorS protein mutated in its C-terminal alternative transmitter. Interestingly, overproduction of the alternative transmitter domain led to in vivo TorR-dependent constitutive expression of the tor operon in a torS+ or torS context. Hence, the TorS alternative transmitter contains the phosphodonor site for TorR. Taken together, our results support a TorS phosphorylation cascade from the classical transmitter to the sensor receiver and the alternative transmitter phosphorylation sites.
J Mol Biol 1997 Apr 11
PMID:Transphosphorylation of the TorR response regulator requires the three phosphorylation sites of the TorS unorthodox sensor in Escherichia coli. 913 10

The TOR proteins, originally identified as targets of the immunosuppressant rapamycin, contain an ATM-like "lipid kinase" domain and are required for early G1 progression in eukaryotes. Using a screen to identify Saccharomyces cerevisiae mutants requiring overexpression of Tor1p for viability, we have isolated mutations in a gene we call ROT1 (requires overexpression of Tor1p). This gene is identical to DNA2, encoding a helicase required for DNA replication. As with its role in cell cycle progression, both the N-terminal and C-terminal regions, as well as the kinase domain of Tor1p, are required for rescue of dna2 mutants. Dna2 mutants are also rescued by Tor2p and show synthetic lethality with tor1 deletion mutants under specific conditions. Temperature-sensitive (Ts) dna2 mutants arrest irreversibly at G2/M in a RAD9- and MEC1-dependent manner, suggesting that Dna2p has a role in S phase. Frequencies of mitotic recombination and chromosome loss are elevated in dna2 mutants, also supporting a role for the protein in DNA synthesis. Temperature-shift experiments indicate that Dna2p functions during late S phase, although dna2 mutants are not deficient in bulk DNA synthesis. These data suggest that Dna2p is not required for replication fork progression but may be needed for a later event such as Okazaki fragment maturation.
Mol Biol Cell 1997 Dec
PMID:Characterization of Saccharomyces cerevisiae dna2 mutants suggests a role for the helicase late in S phase. 939 73

Expression of the Escherichia coli dmsABC operon that encodes a molybdenum-containing DMSO/TMAO reductase is increased in response to anaerobiosis and repressed by nitrate. These changes are mediated by the transcription factors Fnr and NarL respectively. Interestingly, modC strains that are defective in molybdate uptake exhibit impaired anaerobic induction and no nitrate-dependent repression of the dmsABC operon. To determine if the molybdate-responsive transcription factor ModE is involved in this process, a set of dmsA-lacZ operon fusions were constructed and analysed. The pattern of dmsA-lacZ expression in response to anaerobiosis and nitrate addition was identical in both modC and modE strains, thus suggesting a regulatory role for ModE. In vitro studies confirmed that ModE bound the dmsA promoter at a high-affinity site typical of other E. coli ModE operator sites. Mutations in this site abolished ModE binding in vitro and displayed the same phenotype as a modE mutation. In contrast to previously characterized ModE operator sites, which either overlap or are located immediately upstream of the ModE-regulated promoter, the ModE site is centred 52.5 bp downstream of the major dmsA transcript start site. We identified a putative integration host factor (IHF) binding site in the intervening sequence, and in vitro studies confirmed that IHF bound this site with high affinity. Using himA mutants, we confirmed that IHF plays a role in the molybdate-dependent regulation of dmsA-lacZ expression in vivo. This study provides the first example in which ModE affects gene regulation in concert with another transcription factor.
Mol Microbiol 1998 Jan
PMID:Anaerobic regulation of the Escherichia coli dmsABC operon requires the molybdate-responsive regulator ModE. 946 67


1 2 3 4 5 6 7 8 9 10 Next >>