Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.1.21.1 (DNase)
7,655 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Specific beta-adrenergic receptors present in membrane preparations of frog erythrocytes were identified by binding of (-)-[3H]dihydroalprenolol, a potent competitive beta-adrenergic antagonist. The (-)-[3H]dihydroalprenolol binding sites could be solubilized by treatment of a purified erythrocyte membrane fraction with the plant glycoside digitonin but not by treatment with a wide variety of other detergents. The binding sites appeared to be soluble by several independent experimental criteria including (a) failure to sediment of 105,000 X g for 2 hours; (b) passage through 0.22-mu Millipore filters; (c) chromatography on Sepharose 6B gels; and (d) electron microscopy. The soluble receptor sites retained all of the essential characteristics of the membrane-bound sites, namely rapid and reversible binding of beta-adrenergic agonists and antagonists; strict stereospecificity toward both beta-adrenergic agonists and antagonists; appropriate structure-activity relationships; saturability of the sites at low concentrations of ligand; no affinity for alpha-adrenergic drugs, nonphysiologically active catechol compounds, and catecholamine metabolites. Based on gel chromatography in the presence of detergent, the molecular weight of the soluble receptor is estimated to be no greater than 130,000 to 150,000. Equilibrium binding studies indicated a KD for the soluble receptor of 2 nM. Hill coefficients (nH) of 0.77 and curved Scatchard plots suggested the presence of negatively cooperative interactions among the solubilized receptors in agreement with previous findings with the membrane-bound sites. Kinetic studies indicated an association rate constant K1 = 3.8 X 10(6) M-1 min-1 and a reverse rate constant k2 = 2.3 X 10(-3) min-1 at 4 degrees. The kinetically derived KD (k2/k1) of 0.6 nM is in reasonable agreement with that determined by equilibrium studies. The soluble receptors were labile at temperature greater than 4 degrees but could be stabilized with high concentrations of EDTA. Guanidine hydrochloride and urea produced concentration-dependent losses of binding activity which were partially reversible upon dialysis. Trypsin and phospholipase A both degraded the soluble receptors but a variety of other proteases and phospholipases as well as DNase and RNase were without effect. Experiments with group-specific reagents indicated that free lysine, tryptophan, serine, and sulfhydryl groups may be important for receptor binding. These studies suggest that the receptor is probably a protein which requires lipids for functional integrity. Data obtained with the solubilized binding sites are consistent with the contention that these sites represent the physiologically relevant beta-adrenergic receptors which have been extracted from the membranes with full retention of their properties.
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PMID:Solubilization and characterization of the beta-adrenergic receptor binding sites of frog erythrocytes. 0 47

Though DNase does not contain any cysteine residues, incubation of the enzyme with 2-nitro-5-thiocyanobenzoic acid in the presence of Ca2+ at pH values above 7.5 results in an irreversible inactivation of the enzyme. The inactivation also occurs when Ca2+ is replaced by Mg2+, but not in their absence. Amino acid analyses after acid hydrolyses of the completely inactivated ant the native enzymes show no significant differences in composition, including tryptophan and half-cystine residues. However, sodium dodecyl sulfate gel electrophoresis indicates enzyme cleavage by the treatment with 2-nitro-5-thiocyanobenzoic acid. This reagent does not inactivate chymotrypsin and lysozyme, and under conditions where bovine DNase is inactivated, does not inactivate other nucleases such as ribonuclease, snake venom phosphodiesterase, and spleen acid DNase. However, it inactivates malt DNase and can, therefore, be considered a specific inhibitor of DNase I. The inactivation kinetics is pseudo-first order, resembling Michaelis-Menten, with an affinity constant of 16.7 mM. It is the cyano group, not the thionitrobenzoic acid of 2-nitro-5-thiocyanobenzoic acid that reacts to form cyano-DNase.
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PMID:Inactivation of bovine pancreatic DNase by 2-nitro-5-thiocyanobenzoic acid. I. A novel inhibitor for DNase I. 48 54

Nucleosomes and subnucleosomes separated either by sucrose gradient ultracentrifugation or by polyacrylamide gel electrophoresis contain proteins incorporating [3H]tryptophan, i.e. non-histone proteins. The fractions of mononucleosomes MN3 and MN2 are enriched in these proteins as compared to the MN1 fraction. Two-dimensional gel electrophoresis of chromatin digests reveals a number of non-histone proteins comigrating with deoxyribonucleoprotein particles in the first direction (in non-dissociating conditions). A significant fraction of these proteins corresponds to basic non-histone proteins, so-called HMG (high-mobility-group) proteins. Two HMG proteins are present in mononucleosomes MN3 exclusively and three others in mononucleosomes MN3 and MN2. One of them is recovered also in subnucleosomes SN2, and another in SN3 subnucleosome fraction, At least three HMG proteins are rapidly released from the oligonucleosome fractions as well as from the insoluble DNA . protein residue. Thus, they are located in chromatin readily available to DNAase action. Apart from HMG proteins, a number of other non-histone proteins are present in mononucleosomes but their relative content in the oligonucleosome fraction is much higher. The conclusion has been drawn that many non-histone proteins, in particular HMG proteins, interact with linker DNA in chromatin.
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PMID:Non-histone proteins in mononucleosomes and subnucleosomes. 72 Mar 44

Expression of the mtr gene, which encodes a tryptophan-specific transport system in Escherichia coli K-12, is activated by the TyrR protein. Two TyrR protein binding sites (TYR R boxes) are positioned upstream of the -35 promoter region. Mutational and DNase protection studies indicate that TyrR protein binds preferentially to the TYR R box closest to the promoter, and this is essential for activation of gene expression. In the presence of tyrosine and ATP, a second TyrR molecule is able to cooperatively bind to the second box and cause a further increase in the level of activation.
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PMID:Molecular analysis of the TyrR protein-mediated activation of mtr gene expression in Escherichia coli K-12. 193 67

The tryptophan gene (trp) repressor of Escherichia coli has been converted into a site-specific nuclease by covalently attaching it to the 1,10-phenanthroline-copper complex. In its cuprous form, the coordination complex with hydrogen peroxide as a coreactant cleaves DNA by oxidatively attacking the deoxyribose moiety. The chemistry for the attachment of 1,10-phenanthroline to the trp repressor involves modification of lysyl residues with iminothiolane followed by alkylation of the resulting sulfhydryl groups with 5-iodoacetamido-1,10-phenanthroline. The modified trp repressor cleaves the operators of aroH and trpEDCBA upon the addition of cupric ion and thiol in a reaction dependent on the corepressor L-tryptophan. Scission was restricted to the binding site for the repressor, defined by deoxyribonuclease I footprinting. Since DNA-binding proteins have recognition sequences approximately 20 base pairs long, the nucleolytic activities derived from them could be used to isolate long DNA fragments for sequencing or chromosomal mapping.
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PMID:Chemical conversion of a DNA-binding protein into a site-specific nuclease. 282 56

A low frequency of chromosomal gene transfer from Bacillus thuringiensis to Bacillus cereus was detected by cell mating, with a tryptophan marker being the most frequently transferred gene among four that were tested. The process was resistant to DNase and was not mediated by cell filtrates. Among several B. thuringiensis subspecies tested, transfer was best with a derivative of B. thuringiensis subsp. kurstaki HD1, which lost several plasmids. All of the B. cereus recombinants contained at least one plasmid from the donor B. thuringiensis; frequently, it was a plasmid that encoded a protoxin gene. In matings with B. thuringiensis subsp. kurstaki HD1, a 29-megadalton plasmid that contained a ca. 2.5-kilobase region of homology with the chromosome was always transferred. No detectable transfer of chromosomal genes was found in B. thuringiensis subsp. kurstaki HD1 strains lacking this plasmid, suggesting that there may be chromosome mobilization.
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PMID:Transfer of chromosomal genes and plasmids in Bacillus thuringiensis. 282 99

The addition of tryptophan to adult rat hepatocyte cultures stimulated DNA synthesis. The increase in DNA synthesis as measured by 3H-thymidine incorporation into DNA was observed on treatment of the cultures with tryptophan for 48 h but also as short as for 6 h in comparison with control cultures. An increase was also apparent at 30 h which was maintained for up to 48 h post treatment with tryptophan. The increase in DNA synthesis by tryptophan cannot be attributed to cell injury or to increased DNA degradation. Of the degradative enzymes added after harvesting the hepatocytes, only DNase decreased incorporation of 3H-thymidine. The observed effect was specific for tryptophan since treatment with kynurenine, isoleucine, methionine or serine failed to show a significant effect. Pretreatment of cultured hepatocytes with hydroxyurea prevented the tryptophan stimulated increase in DNA synthesis suggesting that the latter was due to replicative and not to reparative DNA synthesis. Experiments performed with the addition of diethylnitrosamine also alluded to tryptophan's role in replicative DNA synthesis. The mechanism of tryptophan-induced DNA synthesis is discussed.
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PMID:Effect of tryptophan on isolated hepatocytes of rats. 288 59

Growth of toxigenic strains of Aspergillus clavatus Des. and Aspergillus flavus Link at 30 degrees C on milled poultry feeds led to a considerable decrease in the protein, oil and crude fibre contents of the feed substrate. A corresponding increase in the free fatty acid fractions of the feeds due to the activities of these microbes was also recorded. Rapid degradation of the feedstuff by both species was recorded at a temperature of 25 degrees C and 30 degrees C and a pH range of 4.8-6.4. When grown on feed infusion broth at 30 degrees C, the highest amounts of mycelial production with sporulation of both fungal species occurred within the 8-day incubation period. A determination of their extra-cellular enzyme profile showed the production of amylases, pectate lyase, cellulases, proteases, lipases, xyalanases, DNase and RNase. All the carbon and nitrogen sources used (except L-sorbose and DL-tryptophan), supported good mycelial growth with sporulation. An optimal C:N ratio of 5.0:4.5 and 7.5:3.0 was recorded for growth and sporulation of A. clavatus. For A. flavus, a C:N ratio of 7.5:4.5 was found best for growth and 5.0:3.0 for sporulation.
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PMID:Toxigenic fungi and the deterioration of Nigerian poultry feeds. 312 47

Trp-155 in bovine DNase A (EC 3.1.4.5) appeared to be unessential for the enzymatic activity for the following reasons: (1) A unique peptide which suggests the environmental difference of Trp-155 was obtained from porcine pancreatic DNase A. (2) Inactivation of the porcine DNase A by NBS modification was fairly paralleled with a decrease in the CD signal, which is characteristic of the "buried" tryptophan in the hydrophobic region (trp-191 in bovine DNase) but not of tryptophans in the hydrophilic portion. Binding of DNase to the poly I: poly C double helix confirmed the important role of this tryptophan.
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PMID:Functional evaluation of tryptophanyl residues of bovine and porcine pancreatic deoxyribonucleases. 345 85

Non-histone chromatin proteins synthesized during chicken embryonic liver development were labeled with [3H]tryptophan and [3H]methionine and characterized by electrophoresis. During embryonic development protein/DNA ratio in chromatin was low (1.30-1.62) but synthesis of non-histone protein was high. Especially one characteristic fraction K (MW 18 000), tightly bound with DNA was preferentially associated with DNAase II sensitive, active transcribed sequences. In 7-day old and adult chicken synthesis of all non-histone proteins was low, fraction K was absent or synthesized only in small amounts in association with non-active sequences, however protein/DNA ratio in chromatin was high (2.30-2.33).
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PMID:Non-histone chromatin protein fractions associated with 'active' chromatin in embryonic chicken liver. 398 96


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