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G Storz

Publications and source records attributed to G Storz.

51 records · Page 3Linked to original sources
PubMed1992

OxyR: a regulator of antioxidant genes.

The study of the bacterial response to hydrogen peroxide has given general insights into how cells defend against deleterious oxidants. Treatment of Salmonella typhimurium and Escherichia coli cells with low doses of hydrogen peroxide results in the induction of 30 proteins and resistance to killing by higher doses of hydrogen peroxide. The expression of nine of the hydrogen peroxide-inducible proteins, including the antioxidant enzymes catalase, glutathione reductase and an alkyl hydroperoxide reductase, is controlled by the positive regulator oxyR. Strains carrying deletions of the oxyR gene are hypersensitive to hydrogen peroxide and have increased levels of spontaneous mutagenesis during aerobic growth. The OxyR protein is homologous to the LysR-NodD family of bacterial regulatory proteins and binds to the promoters of oxyR-regulated genes. The oxidized, but not the reduced, form of the OxyR protein activates transcription of oxyR-regulated genes in vitro, suggesting that direct oxidation of the OxyR protein brings about a conformation change by which OxyR senses an oxidative stress signal and then activates the expression of defense activities.

Antioxidants↗
PubMed1991

High intensity and blue light regulated expression of chimeric chalcone synthase genes in transgenic Arabidopsis thaliana plants.

To establish a genetic system for dissection of light-mediated signal transduction in plants, we analyzed the light wavelengths and promoter sequences responsible for the light-induced expression of the Arabidopsis thaliana chalcone synthase (CHS) promoter fused to the beta-glucuronidase (GUS) marker gene. Transgenic A. thaliana lines carrying 1975, 523, 186, and 17 bp of the CHS promoter fused to the GUS gene were generated, and the expression of these chimeric genes was monitored in response to high intensity light in mature plants and to different wavelengths of light in seedlings. Fusion constructs containing 1975 and 523 bp of CHS promoter sequence behaved identically to the endogenous CHS gene under all conditions. Expression of these constructs was induced specifically in response to high intensity white light and blue light. The response to blue light was seen in the presence of the Pfr form of phytochrome. Fusion constructs containing 186 bp of promoter sequence showed reduced basal levels of expression and only weak stimulation by blue light but were induced significantly by high intensity white light. These analyses showed that the expression of the A. thaliana CHS gene is responsive to a specific blue light receptor and that sequences between -523 and -186 bp are required for optimal basal and blue light-induced expression of this gene. The experiments lay the foundation for a simple genetic screen for light response mutants.

Acyltransferases↗
PubMed1990

Alkyl hydroperoxide reductase from Salmonella typhimurium. Sequence and homology to thioredoxin reductase and other flavoprotein disulfide oxidoreductases.

The DNA sequence of the Salmonella typhimurium ahp locus was determined. The locus was found to contain two genes that encode the two proteins (C22 and F52a) that comprise the S. typhimurium alkyl hydroperoxide reductase activity. The predicted sequence of the F52a protein component of the alkyl hydroperoxide reductase was found to be highly homologous to the Escherichia coli thioredoxin reductase protein (34% identity with many conservative substitutions). The homology was found to be particularly striking in the region containing the redox-active cysteines of the thioredoxin reductase molecule, and among the identities were the redox-active cysteines themselves. Aside from the strong similarity to thioredoxin reductase, overall homology between the F52a protein and other flavoprotein disulfide oxidoreductases such as glutathione reductase, dihydrolipoamide dehydrogenase, and mercuric reductase was found to be rather limited, and the conserved active site segment common to the three proteins was not observed within the F52a protein. However, three short segments that have been implicated in FAD and NAD binding were found to be conserved between the F52a protein and the other disulfide reductases. These results suggest that the alkyl hydroperoxide reductase is the second known member of a class of disulfide oxidoreductases which was represented previously by thioredoxin reductase alone; they also allow the putative assignment of several functional domains.

Amino Acid Sequence↗
PubMed1990

Transcriptional regulator of oxidative stress-inducible genes: direct activation by oxidation.

The oxyR gene positively regulates genes induced by oxidative stress in Salmonella typhimurium and Escherichia coli. Purification of the OxyR protein showed that oxidized but not reduced OxyR activates transcription of oxidative stress-inducible genes in vitro. Conversion between the two forms of OxyR is rapid and reversible. Both the oxidized and the reduced forms of the OxyR protein are capable of binding to three diverse sequences upstream of OxyR-regulated promoters, but the interactions of the two forms of OxyR with the promoter regions are different. The results suggest that direct oxidation of the OxyR protein brings about a conformational change by which OxyR transduces an oxidative stress signal to RNA polymerase.

Bacterial Proteins↗
PubMed1990

The OxyR regulon.

Treatment of Salmonella typhimurium and Escherichia coli cells with low doses of hydrogen peroxide results in the induction of thirty proteins and resistance to killing by higher doses of hydrogen peroxide. The expression of nine of the hydrogen peroxide-inducible proteins, including catalase, glutathione reductase and a novel alkyl hydroperoxide reductase is controlled by the positive regulator oxyR. OxyR is homologous to the LysR-NodD family of bacterial regulatory proteins and binds to the promoters of oxyR-regulated genes. The oxidized but not reduced form of the OxyR protein activates transcription of oxyR-regulated genes in vitro suggesting that oxidation of the OxyR protein brings about a conformational change by which OxyR both senses and transduces an oxidative stress signal to RNA polymerase.

Bacterial Proteins↗
PubMed1990

Bacterial defenses against oxidative stress.

Bacteria treated with low doses of oxidants such as hydrogen peroxide adapt to subsequent high doses of these oxidants by inducing the expression of numerous genes. The study of these genes and the roles they play in defending bacteria against oxidative damage has given general insights into what oxidants are hazardous to cells, what cell constituents are damaged by oxidants, and how cells sense and respond to oxidative stress.

Enterobacteriaceae↗
PubMed1989

Identification and molecular analysis of oxyR-regulated promoters important for the bacterial adaptation to oxidative stress.

The oxyR-encoded regulatory protein, OxyR, acts to induce the synthesis of a family of hydrogen peroxide-inducible proteins in Salmonella typhimurium and Escherichia coli. To further define the mechanism by which oxyR regulates the production of these proteins, we identified, mapped, and characterized oxyR-regulated promoters upstream from the S. typhimurium ahp genes (encoding an alkyl hydroperoxide reductase) and the E. coli katG gene (encoding catalase). A set of ahpC promoter deletions was constructed in vitro and analysis of these deletions revealed the location of sequences that are involved in oxyR-mediated induction of the ahpC gene product. DNase I protection studies of the ahpC promoter region revealed an oxyR-dependent footprint that overlapped the sequences found to be important for oxyR control. E. coli strains containing transcriptional fusions between the katG promoter and the lacZ gene showed strongly increased synthesis of beta-galactosidase in response to hydrogen peroxide treatment. This stimulation was found to be oxyR-dependent. DNase I protection studies of the katG promoter region revealed an oxyR-dependent footprint in the same location relative to the basal promoter elements as was observed with the ahpC promoter. Although both the ahpC and katG promoters were shown to bind the same factor, no strong sequence similarities were found between the two, or between the two and a third oxyR-dependent binding site upstream from the E. coli oxyR gene itself.

Bacterial Proteins↗
PubMed1989

OxyR, a positive regulator of hydrogen peroxide-inducible genes in Escherichia coli and Salmonella typhimurium, is homologous to a family of bacterial regulatory proteins.

The oxyR gene is required for the induction of a regulon of hydrogen peroxide-inducible genes in Escherichia coli and Salmonella typhimurium. The E. coli oxyR gene has been cloned and sequenced, revealing an open reading frame (305 amino acids) that encodes a 34.4-kDa protein, which is produced in maxicells carrying the oxyR clone. The OxyR protein shows homology to a family of positive regulatory proteins including LysR in E. coli and NodD in Rhizobium. Like them, oxyR appears to be negatively autoregulated: an oxyR::lacZ gene fusion produced 5-fold higher levels of beta-galactosidase activity in oxyR null mutants compared to oxyR+ controls, and extracts from an OxyR-overproducing strain were able to protect regions (-27 to +21) of the oxyR promoter from DNase I digestion. DNA sequence analysis of the oxyR2 mutation, which causes overexpression of oxyR-regulated proteins in the absence of oxidative stress, showed that the oxyR2 phenotype is due to a missense mutation (C.G to T.A transition) that changes alanine to valine at amino acid position 234 of OxyR.

Amino Acid Sequence↗
PubMed1989

An alkyl hydroperoxide reductase induced by oxidative stress in Salmonella typhimurium and Escherichia coli: genetic characterization and cloning of ahp.

The ahp genes encoding the two proteins (F52a and C22) that make up an alkyl hydroperoxide reductase were mapped and cloned from Salmonella typhimurium and Escherichia coli. Two classes of oxidant-resistant ahp mutants which overexpress the two proteins were isolated. ahp-1 was isolated in a wild-type background and is dependent on oxyR, a positive regulator of defenses against oxidative stress. ahp-2 was isolated in an oxyR deletion background and is oxyR independent. Transposons linked to ahp-1 and ahp-2 or inserted in ahp mapped the genes to 13 min on the S. typhimurium chromosome, 59% linked to ent. Deletions of ahp obtained in both S. typhimurium and E. coli resulted in hypersensitivity to killing by cumene hydroperoxide (an alkyl hydroperoxide) and elimination of the proteins F52a and C22 from two-dimensional gels and immunoblots. ahp clones isolated from both S. typhimurium and E. coli complemented the cumene hydroperoxide sensitivity of the ahp deletion strains and restored expression of the F52a and C22 proteins. A cis-acting element required for oxyR-dependent, rpoH-independent heat shock induction of the F52a protein was present at the S. typhimurium but not the E. coli ahp locus.

Blotting, Western↗
PubMed1987

Spontaneous mutagenesis and oxidative damage to DNA in Salmonella typhimurium.

Salmonella typhimurium strains containing deletions of oxyR, a positive regulator of defenses against oxidative stress, show 10- to 55-fold higher frequencies of spontaneous mutagenesis compared to otherwise isogenic oxyR+ control strains. The high spontaneous-mutation frequency in oxyR deletion strains is decreased by a factor of 3 when the strains are grown anaerobically. oxyR deletion strains show an increase in small deletion mutations and at least three of the six possible base-substitution mutations (T.A to A.T, C.G to T.A, and C.G to A.T). However, the largest increase in mutation frequency is observed for T.A to A.T transversions (40- to 146-fold), the base-substitution mutation most frequently caused by chemical oxidants. The introduction into oxyR deletion strains of multicopy plasmids carrying the oxyR-regulated genes for catalase (katG) or alkyl hydroperoxide reductase (ahp) results in overexpression of the respective enzyme activities and decreases the number of spontaneous mutants to wild-type levels. The introduction into oxyR deletions of a plasmid carrying the gene for superoxide dismutase (sodA) decreases the mutation frequency by a factor of 5 in some strain backgrounds. Strains that contain a dominant oxyR mutation and overexpress proteins regulated by oxyR show lower spontaneous-mutation frequencies by a factor of 2. These results indicate that oxyR and oxyR-regulated genes play a significant role in defense against spontaneous oxidative DNA damage. The role of oxidative damage to DNA in "spontaneous" mutagenesis is discussed.

Anaerobiosis↗
PubMed1986

Hydrogen peroxide-inducible proteins in Salmonella typhimurium overlap with heat shock and other stress proteins.

Hydrogen peroxide treatment induces the synthesis of 30 proteins in Salmonella typhimurium. Five of these proteins are also induced by heat shock, including the highly conserved DnaK protein. The induction of one of these five proteins by heat shock is dependent on oxyR, a positive regulator of hydrogen peroxide-inducible genes, while the induction of the other four by heat shock is oxyR independent. Five of the 30 hydrogen peroxide-inducible proteins have been identified, and their structural genes have been mapped. Other stresses such as nalidixic acid, ethanol, or cumene hydroperoxide treatment also induce subsets of the 30 hydrogen peroxide-inducible proteins as well as additional proteins. Hydrogen peroxide-inducible proteins are shown to be largely different from those proteins induced by aerobiosis. In addition, the expression of the katG (catalase) gene is shown to be regulated by oxyR at the level of mRNA.

Adaptation, Physiological↗
PubMed1982

[A new test-strip for checking blood-sugar levels].

Blood sugar levels in 228 EDTA-treated venous blood samples were measured in the laboratory by a new test-strip (Visidex) and the hexokinase reference method. There was good agreement between the two, with a linear correlation of r = 0.92 and a regression line with a slope of 0.98. 97.8% of all values deviated by less than one concentration range from the reference values. At low glucose concentrations the median of the absolute differences between the two methods was 9.5 mg/dl. Over the whole concentration range of 20-800 mg/dl the mean deviation from the reference values was between 14.4 and 32.6 mg/dl. The results indicate that the Visidex test-strip method is suitable for the visual estimation of blood sugar values.

Blood Glucose↗
PubMed1982

Evaluation of a quantitative solid phase reagent system for determination of blood analytes. Experiences with the analytes: LDH, bilirubin, BUN, glucose, and uric acid.

In the first part of the Seralyzer system evaluation the precision and accuracy was studied with a total of 1245 clinical specimens, various commercial control sera, and pooled human sera. The calculated overall precision (between-run, and within-run) and day-to-day precision (% CV) was found to be within 3.0 to 5.4 for glucose, 2.8 to 7.1 for BUN, 1.5 to 6.2 for uric acid, 5.3 to 7.5 for bilirubin, and 3.2 to 8.6 for LDH. The clinical values are in agreement with values from respective comparative methods, as indicated by the regression statistics. The analysis of Seralyzer accuracy data using quality control sera showed in some cases a between-method difference. Supporting studies simulating additional important clinical situations showed that the clinical values for BUN, glucose, and uric acid of approximately 200 specimens from the emergency ward correlated with the respective comparative method values. In this phase of the study we verified that the instrument calibration was stable for a 24-hour period and that there is no effect of module (test) change on precision of Seralyzer determinations. The intra- and inter-laboratory performance in general practitioners' laboratories could be demonstrated using quality control sera.

Bilirubin↗
PubMed1981

[Determination of blood constituents with dry reagent carriers. Comparison with wet chemical tests (author's transl)].

Quantitative measurement of blood constituents (glucose, uric acid, urea-N) on dry reagent carriers was compared with corresponding wet-chemical methods. There was a good correlation (r greater than 0.95) and excellent linear regression with small scatter between the two methods for the three constituents. The dry test has proved to be a precise, simple, rapid and economic method, especially suitable for the practitioner and emergency laboratory.

Blood Glucose↗