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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The redox interconversion of Escherichia coli glutathione reductase has been studied both in situ, with permeabilized cells treated with different reductants, and in vivo, with intact cells incubated with compounds known to alter their intracellular redox state. The enzyme from toluene-permeabilized cells was inactivated in situ by NADPH, NADH, dithionite, dithiothreitol, or GSH. The enzyme remained, however, fully active upon incubation with the oxidized forms of such compounds. The inactivation was time-, temperature-, and concentration-dependent; a 50% inactivation was promoted by just 2 microM NADPH, while 700 microM NADH was required for a similar effect. The enzyme from permeabilized cells was completely protected against redox inactivation by GSSG, and to a lesser extent by dithiothreitol, GSH, and NAD(P)+. The inactive enzyme was efficiently reactivated in situ by physiological GSSG concentrations. A significant reactivation was promoted also by GSH, although at concentrations two orders of magnitude below its physiological concentrations. The glutathione reductase from intact E. coli cells was inactivated in vivo by incubation with DL-malate, DL-isocitrate, or higher L-lactate concentrations. The enzyme was protected against redox inactivation and fully reactivated by diamide in a concentration-dependent fashion. Diamide reactivation was not dependent on the synthesis of new protein, thus suggesting that the effect was really a true reactivation and not due to de novo synthesis of active enzyme. The glutathione reductase activity increased significantly after incubation of intact cells with tert-butyl or cumene hydroperoxides, suggesting that the enzyme was partially inactive within such cells. In conclusion, the above results show that both in situ and in vivo the glutathione reductase of Escherichia coli is subjected to a redox interconversion mechanism probably controlled by the intracellular NADPH and GSSG concentrations.
Mol Cell Biochem 1985 Oct
PMID:Redox interconversion of Escherichia coli glutathione reductase. A study with permeabilized and intact cells. 390 6

Bleomycin (BLM) is an antitumor drug which interacts with and damages DNA. We have reported a repair response dependent on DNA polymerase I in toluene-treated Escherichia coli. We report here that DNA polymerase III can also catalyze a repair response in toluene-treated E. coli following exposure to BLM. Polymerase III-mediated synthesis differs because it is ATP-dependent, whereas polymerase I-mediated repair synthesis is not. Polymerase III repair synthesis is independent of replicative synthesis, as demonstrated in a polA-, dnaBts strain, or use of Novobiocin to inhibit replication, and replication persists in the presence of repair synthesis. It appears that ATP-dependent repair synthesis in response to BLM is also present in polA+ strains. Repair synthesis does not require the uvrA gene product.
Mol Gen Genet 1980
PMID:DNA polymerase III-dependent repair synthesis in response to bleomycin in toluene-treated Escherichia coli. 616 Mar 70

A class of rpoB mutations is described which suppresses replication and transcription deficiency in gyrB-ts mutants shifted to a nonpermissive temperature. The compensatory effect of an altered subunit B of RNA polymerase (rpoB) for the gyrB defect, indicates that transcription is a primary target of the B subunit of DNA gyrase. One gyrB mutation (gyrB402-ts) shows deficiency in chromosome elongation at the nonpermissive temperature, both in vivo and in cells permeabilized with toluene. It is therefore concluded that the gyrB polypeptide functions at least dually in replication; first, at the level of transcription initiation and second, at the level of chain polymerization.
Mol Gen Genet 1983
PMID:The gyrB gene product functions in both initiation and chain polymerization of Escherichia coli chromosome replication: suppression of the initiation deficiency in gyrB-ts mutants by a class of rpoB mutations. 619 15

A toluene-permeabilized cell system was established to examine the transcription of certain RNAs regulated during the cell cycle in Chlamydomonas reinhardi. The incorporation of [alpha-32P]UTP into RNA which hybridizes to specific cloned cDNA, such as beta-tubulin, indicates that the cell cycle pattern of RNA accumulation may be controlled, in part, by differential transcription.
Mol Cell Biol 1983 Aug
PMID:Analysis of transcription during the cell cycle in toluenized Chlamydomonas reinhardi cells. 662 39

The effect of modification of carboxylic groups of phenylalanyl-tRNA synthetase by p-toluene sulfonate N-cyclohexyl-N'-beta-(4-methylmorpholine) ethylcarbodiimide (CMEC) on the activity of the enzyme was investigated. It was shown that modification of two moles of carboxylic groups per mole of the enzymes leads to the diminution of negative charge of the enzyme and to inactivation in ATP-[32P]PPi-exchange and aminoacylation reactions. The inactivation is completely reversed by mild alkaline hydrolysis. ATP in concentration 2 X 10(-4) M partially protects the enzyme against inactivation, protective effect being stimulated by Mg2+ and 0.4-0.7 moles of carboxylic groups per mole of the enzyme are protected against inactivation is observed although the depth of modification is increased. Other substrates do not have protective effect. Modification of the enzyme by CMEC increases Kdiss value of [14C]-Phe-tRNA enzyme complex and Km value for tRNAPhe in aminoacylation by factor of three. Vmax for all substrates in both aminoacylation and leads to 40% increase of Hill's coefficient for ATP in ATP-[32P]PPi-exchange reaction but not in aminoacylation. The carboxylic groups modified by CMEC are assumed to take part in ATP recognition and in catalysis of the ATP conversion and in catalysis of transfer of activated amino acid residues on tRNA.
Mol Biol (Mosk)
PMID:[Role of the carboxylic groups in interaction of phenylalanyl-tRNA synthetase with substrates]. 703 45

A 3 kb DNA region upstream of the toluene degradation (tod) genes, todFC1C2BADEGIH, in Pseudomonas putida F1 (PpF1) was sequenced. Two divergently arranged open reading frames, todR and todX, were identified. A toluene-inducible promoter was localized in front of todX, and the transcription start point was mapped. This promoter is probably responsible for the expression of all tod structural genes. TodX was found to be a membrane protein. Its predicted amino acid sequence (453 residues; M(r) 48,265) exhibits considerable similarity with the FadL protein of Escherichia coli, an outer membrane protein required for binding and transport of long-chain fatty acids. An apparent function of TodX is likely to be involved in facilitating the delivery of exogenous toluene inside the PpF1 cells. The sequence of TodR (100 residues) exhibits extensive homology with the DNA-binding domain of transcriptional activators of the LysR family, but todR was found to have a negligible role in tod gene regulation.
Mol Gen Genet 1995 Mar 10
PMID:Identification of a membrane protein and a truncated LysR-type regulator associated with the toluene degradation pathway in Pseudomonas putida F1. 753 76

In the presence of toluene, xylenes and other structural analogues, the regulatory protein XylR, of the family of transcriptional regulators which act in concert with the sigma 54 factor, activate the promoter Pu of the TOL (toluene degradation) plasmid pWWO of Pseudomonas putida. Amino acid changes Val-219-Asp and Ala-220-Pro, introducing a proline kink at the hinge region between the N-terminal A domain and the central portion of XylR, resulted in a semi-constitutive phenotype which mimicked the activating effect of aromatic inducers. This phenotype was further exacerbated by inserting extra amino acid residues within the same inter-domain region. A truncated XylR protein devoid of the signal-receiving, amino-terminal portion of the protein stimulated the cognate promoter Pu at high levels independently of inducer addition, both in Escherichia coli and in Pseudomonas putida. Replacement of the amino-terminal domain by a heterologous peptide derived from the MS2 virus polymerase resulted in a hybrid protein still able to bind DNA to the same extent in vivo as XylR, but unable to stimulate transcription. These data indicate that a key event in the activation of XylR by toluene/xylenes is the release of the repression caused by the A domain of the protein on surfaces located at the central domain of the regulator.
Mol Microbiol 1995 Apr
PMID:Activation of the transcriptional regulator XylR of Pseudomonas putida by release of repression between functional domains. 756 83

Endothelial cells have been shown to generate primary oxygen-centered free radicals (hydroxyl, superoxide anion) during post-anoxic reoxygenation, but little evidence is available concerning subsequent initiation of lipid peroxidative injury in this model. Electron spin resonance (ESR) spectroscopy with alpha-phenyl-N-tert-butylnitrone (PBN) spin trapping was used to monitor lipid peroxidation (LPO)-derived free radicals formed by cultured bovine aortic endothelial cell suspensions exposed (37 degrees C) to anoxia (A, 45 min, N2 gas) and reoxygenation (R, 15 min, 95% O2/5% CO2). In some studies, superoxide dismutase (SOD, 10 micrograms/ml) was introduced just prior to R to assess the effects of this primary free radical scavenger on LPO-derived free radical production. At various times, aliquots were removed and PBN was introduced to either the cell suspension aliquot (8 mM PBN final, 1 min), or to the corresponding cell-free filtrate (60 mM PBN final), prior to extraction with toluene and ESR spectroscopy. A LPO-derived alkoxyl radical adduct of PBN (PBN/RO., hyperfine splitting alpha N = 13.63 G and alpha H = 1.94-1.98 G) was observed during R using both trapping procedures, with maximal production at 4-5 min and a second minor peak at 10 min. SOD effectively reduced PBN/RO. production and improved viability of A/R cells. In parallel studies, lipid hydroperoxide production was assessed in lipid extracts of A/R cells by high-performance liquid chromatography. Their separation profiles revealed a peak of oxidized lipid occurring between phosphatidylethanolamine (PE) and phosphatidylcholine (PC) in samples taken at 4-5 min and 10 min of R. Resolubilizing cell lipid extracts in oxygen-free benzene containing cobalt (II) acetylacetonate and PBN led to alkoxyl radical production, but only in the oxidized lipid samples, confirming the presence of hydroperoxides. These results suggest that A/R leads to primary free radical induced-lipid peroxidative injury to endothelial cells, as indicated by alkoxyl radical production originating from oxidized membrane phospholipids.
J Mol Cell Cardiol 1995 Jan
PMID:Phospholipid hydroperoxides are precursors of lipid alkoxyl radicals produced from anoxia/reoxygenated endothelial cells. 776 Mar 59

BDF1 mice were exposed in inhalation chambers to benzene (900 ppm, 300 ppm) and/or toluene (500 ppm, 250 ppm) 6 hr per day, 5 days per week, for up to 8 weeks. Benzene alone induced a slight anemia after 4 and 8 weeks and a reduction of BFU-E and CFU-E numbers in the marrow. The coexposure to toluene reduced the degree of anemia. These results confirm previous studies where toluene was found to reduce benzene toxicity. This protective effect was most pronounced when DNA damage was studied in peripheral blood cells, bone marrow, and liver using the single cell gel (SCG) assay. With benzene alone, either with 300 or 900 ppm, a significant increase in DNA damage was detected in cells sampled from all three organs. Toluene alone did not induce a significant increase in DNA damage. The coexposure of benzene and toluene reduced the extent of DNA damage to about 50% of benzene alone. This result is considered a clear indication for a protective effect of toluene on the genetic toxicity of benzene.
Environ Mol Mutagen 1994
PMID:Reduction of benzene toxicity by toluene. 785 40

TOL plasmid pWW0 of Pseudomonas putida contains two operons that specify a pathway for the degradation of aromatic hydrocarbons. The upper pathway operon encodes the enzymes for the oxidation of toluene/xylenes to benzoate/toluates, and the metacleavage pathway operon encodes the enzymes for the further oxidation of these compounds to Krebs cycle intermediates. Their expression is controlled by the gene products of two divergently transcribed regulatory genes, xyIR and xyIS. The XyIR protein, which belongs to the NtrC family of regulators, is expressed from two tandem promoters and autoregulates its synthesis. XyIR stimulates transcription from the xyIS gene promoter (Ps) and the upper pathway operon promoter (Pu) in the presence of pathway substrates. Both promoters are sigma 54 dependent, and Pu also requires the presence of integration host factor (IHF) for activation of transcription. Binding sites for XyIR and IHF in the Pu promoter and for XyIR in the Ps promoters have been defined. The XyIS protein, which belongs to the AraC family of regulators, stimulates transcription from the meta-cleavage pathway operon promoter (Pm) in the presence of benzoates. The effector binding pocket and DNA-binding region of XyIS have been defined through the isolation of mutants that exhibit altered effector specificity and modified transcriptional patterns, respectively. Expression of the meta-cleavage pathway operon is also induced by xylene-activated XyIR protein via a cascade regulatory system in which this protein, in combination with sigma 54, stimulates the expression from the xyIS promoter.(ABSTRACT TRUNCATED AT 250 WORDS)
Mol Microbiol 1993 Sep
PMID:Transcriptional control of the Pseudomonas putida TOL plasmid catabolic pathways. 793 20


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