Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.1.25.1 (deoxyribonuclease)
 1,471 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A soluble somatostatin-binding protein was detected in the cytosol fractions of various rat, human and bovine tissues. Maximum binding occurred at pH8.0-8.5 and was Ca(2+)-dependent. The specific binding of somatostatin per 10mug of cytosol protein from 12 rat tissues ranged between 36 and 15%, and 3% for peripheral blood cells. There was also substantial binding in cytosol from human anterior pituitary and liver, and bovine anterior pituitary. The specific binding in rat and human plasma in the presence of EDTA was only 1%. Gel filtration suggested a molecular weight of approx. 80000 for the somatostatin-binding protein from several sources. Exposure of the binding protein to trypsin eliminates somatostatin-binding activity but ribonuclease and deoxyribonuclease have no effect. The binding protein is thermolabile, ethanol-precipitable, and not completely specific for somatostatin. Bound (125)I-labelled [Tyr(1)]somatostatin is not easily displaced by excess of unlabelled somatostatin. The effects of dithiothreitol and mercaptoethanol on the binding of (125)I-labelled [Tyr(1)]somatostatin to the binding protein suggests that binding involves two sequential steps, first loose binding, then disulphide linkage. Since semipurified somatostatin-binding protein causes a dose-related inhibition of the binding of (125)I-labelled [Tyr(1)]somatostatin in radioimmunoassays for somatostatin, estimates of somatostatin content of tissue extracts by radioimmunoassay in some cases may be spuriously high. It is not yet clear whether the binding protein is a true cytosol protein or an easily solubilized membrane protein.
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PMID:Properties of soluble somatostatin-binding protein. 2 54

T4 endonuclease V recognizes thymine photodimers in DNA duplexes and, in a two-step reaction, cleaves the glycosyl linkage of the 5'-side thymidine and the phosphodiester linkage. To determine the amino acid residues responsible for binding thymine photodimers, a photoaffinity reagent, 4-(1-azi-2,2,2-trifluoroethyl)-benzoate, was linked to the aminoalkylphosphonate of a thymine photodimer in a 14-mer duplex. The reactive substrate was treated with the enzyme under UV light (365 nm). The nascent enzyme and the modified enzyme were treated with lysyl endopeptidase, and the peptide maps were compared. Three peptides from the C terminus were found to interact with the reactive oligonucleotide to various extents. The three modified peptides were isolated and analyzed by Edman degradation. The amino acid residues Gly-133, Tyr-129, and Thr-89 were partially linked with the reactive substrate and may be involved in the binding of thymine photodimers.
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PMID:Photoaffinity labeling of T4 endonuclease V with a substrate containing a phenyldiazirine derivative. 163

Previous structure/function analyses of the DNA repair enzyme, T4 endonuclease V, have suggested that the extreme carboxyl portion of the enzyme is associated with pyrimidine dimer-specific binding (Recinos and Lloyd, and Stump and Lloyd, Biochemistry 27:1832-1838 and 1839-1843, 1988, respectively). Within the final 11 amino acids there are 5 aromatic, 2 basic, and no acidic residues and it has been proposed that these residues stack with and electrostatically interact with the kinked DNA at the site of a pyrimidine dimer. The role of the tyrosine residue at position 129 has been investigated by oligonucleotide site-directed mutagenesis in which the codon for Tyr-129 has been altered to reflect conservative changes of Trp and Phe and more dramatic changes of Ser, a stop codon, deletion of the codon or introduction of a frameshift. Both changes to the aromatic amino acids resulted in proteins which accumulated well in E. coli and not only significantly enhanced the UV survival of repair-deficient cells but also complemented a defective denV gene within UV-irradiated T4 phage. Partially purified preparations of the Tyr-129----Trp and Tyr-129----Phe mutants were assayed for their ability to processively incise UV-irradiated plasmid DNA (a nicking reaction carried out at low 25 mM salt concentrations). The mutant enzymes Tyr-129----Phe and Tyr-129----Trp displayed a 1000% and 500% enhanced specific nicking activity, respectively. These reactions were also shown to be completely processive. Assays performed at higher (100 mM) salt concentrations reduced the specific activities of the mutant enzymes approximately to that of wild type for the Tyr-129----Phe mutant and to 20% that of wild type for the Tyr-129----Trp mutant.
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PMID:Site-directed mutagenesis of the T4 endonuclease V gene: mutations which enhance enzyme specific activity at low salt concentrations. 269 26

T4 endonuclease V incises DNA at the sites of pyrimidine dimers through a two-step mechanism. These breakage reactions are preceded by the scanning of nontarget DNA and binding to pyrimidine dimers. In analogy to the synthetic tripeptides Lys-Trp-Lys and Lys-Tyr-Lys, which have been shown to be capable of producing single-strand scissions in DNA containing apurinic sites, endonuclease V has the amino acid sequence Trp-Tyr-Lys-Tyr-Tyr (128-132). Site-directed mutagenesis of the endonuclease V gene, denV, was performed at the Tyr-129 and at the Tyr-129 and Tyr-131 positions in order to convert the Tyr residues to nonaromatic amino acids to test their role in dimer-specific binding. The UV survival of repair-deficient (uvrA recA) Escherichia coli cells harboring the denV N-129 construction was dramatically reduced relative to wild-type denV+ cells. The survival of denV N-129,131 cells was indistinguishable from that of the parental strain lacking the denV gene. The mutant endonuclease V proteins were then characterized with regard to (1) dimer-specific nicking activity, (2) apurinic nicking activity, and (3) binding affinity to UV-irradiated DNA. Dimer-specific nicking activity and dimer-specific binding for both denV N-129 and N-129,131 were abolished, while apurinic-specific nicking was substantially retained in denV N-129,131 but was abolished in denV N-129. These results indicate that Tyr-129 and Tyr-131 positions of endonuclease V are at least important in pyrimidine dimer-specific binding and possibly nicking activity.
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PMID:Site-directed mutagenesis of the T4 endonuclease V gene: role of tyrosine-129 and -131 in pyrimidine dimer-specific binding. 328 78

Isolated nuclei incubated with [14C]protein hydrolysate are shown to incorporate labelled amino acids into the acid-insoluble fraction. Purified chromatin and the complex of DNA with firmly bound proteins possess similar ability. The optimum pH of the reaction is 6.5-7.0, 2 mM MgCl2 stimulates incorporation, the temperature optimum is 37-40 degrees C. Chloramphenicol depresses incorporation by 70%, puromycin by 40%, cycloheximide does not affect the chromatin activity. Incorporation does not depend on the presence of ATP or GTP, and is substantially inhibited by deoxyribonuclease but not by ribonuclease treatment of chromatin or of the nuclei. Specific activity of firmly bound chromatin non-histone proteins is higher than that of labile bound ones; histones are not labelled. After pronase treatment of proteins radioactivity changes to an acid-soluble state. The molecular weight of isolated labelled polypeptides is about 6000 as shown by gel filtration and the analysis of NH2-terminal amino acids. Labelled polypeptides firmly bound to DNA consist of 7-10 amino acids. Specific activity of proteins firmly bound to DNA increases linearly with the time of incubation of chromatin with [14C]protein hydrolysate, the activity curve of labile bound non-histone proteins has a distinct sygmoid character. The polypeptide-synthesizing activity of rat liver chromatin increases between 9 h and 21 h after partial hepatectomy. Irradiation with 800 rads 30 min before the operation prevents activation of amino acid incorporation. From nine amino acids studied alanine, methionine, lysine, tyrosine and arginine are not incorporated in the system described. Glutamic acid is polymerized most effectively. Glutamine, asparagine and glycine are incorporated 7-8 times less. The data are given indicating that the incorporation is not random when an amino acid mixture is present. Preincubation of chromatin with NAD+ but not with its analogues increases the polypeptide-synthesizing activity of chromatin. The activation is prevented by thymidine and nicotinamide. Storage (18 h at 2-4 degrees C) brings about a complete loss of the polypeptide-synthesizing activity of chromatin. The ability of 'old' chromatin to incorporate amino acids can be restored by preincubating it with NAD+. Storage of chromatin in the presence of 5 mM adenosine 3',5'-monophosphate (cAMP) does not result in decrease of the polypeptide-synthesizing activity. It is assumed that poly-(ADP-ribose) is the energy source for amino acid activation in the system described.
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PMID:Polypeptide-synthesizing activity of eukaryotic chromatin. Properties, dependence on poly(ADP-ribose) and connection with the cell cycle. 737 37