Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.1.27.5 (RNase)
 17,967 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

1. The isolated nuclei of the slime mould Physarum polycephalum contain an enzyme that will incorporated [adenine-3H] NAD+ into an acid-insoluble product, which is shown to be poly(ADP-ribose). 2. This incorporation has an optimum pH of 8.2 and a temperature optimum below 10degreesC. 3. Optimum stimulation is given by 15 mM-Mg2+. 4. 2-Mercaptoethanol or dithiothreitol also stimulates the incorporation, the latter at an optimum concentration of about 1 mM. 5. Under optimum conditions the Km value for the reaction is 0.28 mM at 15degreesC. Nicotinamide inhibits the incorporation with a Ki of 5.7 muM. 6. Exogenous DNA stimulates the incorporation by about 100%. 7. Preincubation of the nuclei with deoxyribonuclease, but not with ribonuclease, almost completely inactivates the incorporation of NAD+. 8. The enzyme is unstable at both 0degrees and 15degreesC in the absence of dithiothreitol. The presence of dithiothreitol at a concentration of 1 mM stabilizes the enzyme at both these temperatures. 9. The activity of this enzyme per nucleus was shown in three separate experiments to fall by about one-half in early S phase and then to rise to its pre-mitotic value after about 3 h, that is in late S phase. 10. The possible physiological function of this enzyme system is discussed.
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PMID:Poly(adenosine diphosphate ribose) polymerase in Physarum polycephalum. 23 97

The existence of a DNA-dependent protein methylase activity without any concomitant DNA methylase activity was demonstrated in bull seminal plasma. The enzyme utilized S-adenosyl-L-methionine as a methyl donor, and endogenous seminal plasma protein as the substrate. There was no demonstrable enzyme activity when the seminal plasma was preheated at 100 degrees for 10 min, or when the enzyme reaction mixture was incubated at 4 degrees. The protein methylase required a heterologous DNA source, had optimal activity at pH 8.1, and was enhanced in the presence of Mg2+, NH4+, and reduced glutathione. After the methylated protein product was separated from DNA by extraction with 0.2 M HCl, the incorporated radioactivity was shown to be totally solubilized by incubating the protein either with Pronase or 1 M NaOH, while RNase and DNase had no effect. Approximately 70% of the enzymatically synthesized amino acids in the protein product were tentatively identified as O-methylated amino acid ethers by virtue of their elution from a Dowex 50 H+ column with 0.2 M pyridine, and their stability to acid and base hydrolysis. The partially purified methylated product was shown by Sephadex G-50 chromatography to consist of three distinct radioactive proteins with molecular weights of approximately 21,000, 15,000, and 10,000.
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PMID:DNA-dependent protein methylase activity in bull seminal plasma. 24 Mar 99

A new ribonuclease has been isolated from Escherichia coli. The enzyme is present in the 100,000 times g supernatant fraction and has been purified over 200-fold. Studies of the enzyme reveal that: 1. The enzyme shows a marked preference for oligoribonucleotides; indeed, the reaction rate is inversely proportional to the chain length of the substrate. The enzyme does not attack polynucleotides even at high concentrations of enzyme and has no detectable DNase activity. 2. The enzyme is stimulated strongly by Mn2+, less strongly by Mg2+, and not at all by Ca2+ and monovalent cations. 3. The enzyme is purified free of RNase I, RNase II, RNase III, polynucleotide phosphorylase, and other known ribonucleases of E. coli. The enzyme displays identical properties when isolated from mutants of E. coli that are deficient in the above ribonucleases. 4. The enzyme has a marked thermostability, a point of further distinction from RNase II.
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PMID:A novel oligoribonuclease of Escherichia coli. I. Isolation and properties. 24 Aug 24

Chlamydomonas reinhardtii cells treated with toluene at 0 degrees C and 25 degrees C incorporate ribonucleoside triphosphates (NTPs) into chloroplast RNA at 25 degrees C and also at 35 degrees C. The incorporation requires all four NTPs and Mg2+, and is completely inhibited by DNase, RNase, actinomycin D (40 microgram/ml) and rifampicin (350 microgram/ml). However, the incorporation is almost totally insensitive to both alpha-amanitin and streptolydigin at 200 microgram/ml.
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PMID:Synthesis of chloroplast ribonucleic acid in Chlamydomonas reinhardtii toluene-treated cells. 25 50

Chromatin from trout testis at an early stage of development was digested with DNase II (deoxyribonucleate 3'-oligonucleotidohydrolase; EC 3.1.4.6), and the solubilized products were fractionated into Mg2+-soluble and -insoluble components. An examination of the histones from these fractions by one- and two-dimensional polyacrylamide gels showed that the highly acetylated species of histone H4 (di-, tri-, and tetra-acetylated) were associated mainly with the Mg2+-soluble material. Digestion of this chromatin fraction with pancreatic ribonuclease converted more than half of it to an insoluble state, and the acetylated H4 remained associated with the precipitated fraction. No changes in the other histones were noted, but two other basic proteins were also found to be associated with the Mg2+-soluble fraction. Since this fraction is enriched in transcribing gene sequences, it is concluded that the histone H4 of active genes is present in a highly acetylated state.
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PMID:Acetylated histone H4 is preferentially associated with template-active chromatin. 27 72

Membranes prepared from A-431 human epidermoid carcinoma cells retained the ability to bind 125I-labeled epidermal growth factor (EGF) in a specific manner. In the presence of [gamma-32P]ATP and Mn2+ or Mg2+, this membrane preparation was capable of phosphorylating endogenous membrane components, including membrane-associated proteins; the major phosphorylated amino acid residue detected in partial acid hydrolysates was phosphothreonine. The binding of EGF to these membranes in vitro resulted in a severalfold stimulation of the phosphorylation reaction; again, the major phosphorylated amino acid residue detected in partial acid hydrolysates was phosphothreonine. Membrane-associated dephosphorylation reactions did not appear to be affected by EGF. The phosphorylation reaction was not stimulated by cyclic AMP or cyclic GMP in the absence or presence of EGF. The phosphorylation system of the membrane was able to utilize [gamma-32P]GTP in both the basal and EGF-stimulated reactions. The enhanced membrane phosphorylation was specific for EGF and its derivatives; a wide variety of other peptide hormones were ineffective. The A-431 membrane preparation also was capable of phosphorylating exogenous proteins, such as histone, phosvitin, and ribonuclease, by a process which was stimulated by EGF. These findings suggest that one of the biochemical consequences of the binding of EGF to membranes is a rapid activation of a cyclic AMP-independent phosphorylating system.
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PMID:Rapid enhancement of protein phosphorylation in A-431 cell membrane preparations by epidermal growth factor. 31 92

We investigated the ribonucleolytic breakdown of poly(U), poly(A), RNA trascribed from calf thymus DNA with E. coli RNA polymerase, ribosomal RNA, tRNA and mengovirus RNA by an enzyme fraction obrained from a postribosomal supernatant of Ehrlich ascites tumor cells. The single-stranded homopolyribonucleotides are preferentially degraded by the enzyme fraction with the production of ribonucleoside 5'-monophosphates. The RNase activity is completely dependent on the presence of Mg2+ ions and is highest at Mg2+ and K+ concentrations optimal for cell-free protein synthesis. Ribonucleoside 5'-monophosphates, ribonucleoside 2'(3')-monophosphates, ribonucleoside 2'(3'),5'-bisphosphates and transition state analogs consisting of vanadyl sulfate and either ribonucleosides or ribonucleoside 5'-monophosphates in a molar ratio 1:1 inhibit the ribonucleolytic activity of the enzyme fraction. The ribonucleoside 2'(3'),5'-bisphosphates and the transition state analogs are the most effective inhibitors. However, only in the presence of ribonucleoside 2'(3'),5'-bisphosphates a concomitant stimulation by 50 to 60% of poly(U)-directed polyphenylalanine synthesis is observed; all the other RNase inhibitors tested also inhibit polypeptide synthesis. The results of preliminary experiments show that poly(U) and ribonucleoside 2'(3'),5'-bisphosphates are well suited as ligands for affinity chromatography of ribonucleases from Ehrlich ascites tumor cells.
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PMID:Inhibition of ribonucleases by ribonucleotides and transition state analogs in cell-free extracts from Ehrlich ascites tumor cells. 32 84

A nuclease (RNase D) that can recognize structurally altered transfer RNA molecules has been partially purified from Escherichia coli. The enzyme acts poorly on intact tRNA and is inactive with the synthetic polyribonucleotides, poly(A), poly(U), or double-stranded poly(A).poly(U). The enzyme requires Mg2+ for activity and is stimulated by the monovalent cations, K+ and NH4+. The products of the reaction are 5'-mononucleotides. The molecular weight of the protein is about 60,000 as judged by Sephadex G-100 chromatography. The enzyme does not correspond to any known E. coli ribonuclease and may represent an intracellular scavenging mechanism for denatured tRNAs and other inactive RNA molecules.
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PMID:Identification of an Escherichia coli nuclease acting on structurally altered transfer RNA molecules. 34 22

The biosynthesis of bacteriophage T4 tRNAPro, tRNASer, and tRNAIle requires enzymatic removal of extra nucleotides from the 3' terminus of the respective precursor RNAs. A ribonuclease activity capable of catalyzing such reactions has been partially purified from uninfected Escherichia coli using an artificial precursor RNA as substrate. A number of ribonuclease activities were resolved during purification. Use of E. coli strain BN, a mutant known to be deficient in the relevant ribonuclease activity, permitted us to identify it in wild-type cells. This activity was designated the BN ribonuclease. BN ribonuclease had an apparent molecular weight of 35,000 as measured by Sephadex gel filtration. Mg2+ was required for activity, which was optimal at [Mg2+] of 2mM. Activity did not require monovalent cations K+ or Na+. BN ribonuclease was less efficient at removing extra residues in the biosynthesis of tRNASer and tRNAIle than in the biosynthesis of tRNAPro.
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PMID:An Escherichia coli ribonuclease which removes an extra nucleotide from a biosynthetic intermediate of bacteriophage T4 proline transfer RNA. 36 22

A second major species of leucine tRNA, tRNA Leu UAG (formerly designated tRNA Leu CUA) was purified from baker's yeast in a three-step procedure entailing BD-cellulose chromatography in the presence and absence of Mg2+ and Sephadex G-100 gel filtration. Results of aminoacylation and partial RNase T1 digestion experiments showed that this tRNA retains a native conformation under conditions that denature yeast tRNA Leu m5CAA (tRNA3 Leu). The primary structure of baker's yeast tRNA Leu UAG was elucidated by application of sensitive radioactive isotope derivative ("postlabeling") methods. Complete RNase T1 and A and partial RNase U2 fragments, prepared from non-radioactive tRNA and 5'-half and 3'-half molecules, were separated by two-dimensional polyethyleneimine-cellulose anion-exchange thin-layer chromatography and isolated by a novel micropreparative procedure affording high yields of these compounds in sufficient purity for subsequent tritium derivative analysis. Base composition and sequence of oligonucleotides were analyzed by tritium derivative methods. Molar ratios of the fragments were determined from the radioactivity of 3H-labeled nucleoside trialcohols in combination with base analysis. 2'-O-Methylated guanosine was characterized using the [gamma-32P]ATP/polynucleotide kinase reaction. The analysis of classical complete and partial RNase digests by the tritium derivative methods yielded the complete nucleotide sequence of the tRNA. A total of about 20 A260 units of the RNA was used for analysis, i.e. considerably less material than required for conventional spectrophotometric analysis. A different sequencing approach, consisting of a combination of "readout sequencing" with tritium sequencing of complete RNase T1 and A fragments, was applied to the 3'-half molecule. The 3'-half molecule was labeled with 32P at its 5' terminus, partially degraded with RNase T1, U2, and Phy1 and with alkali, and subjected to polyacrylamide gel electrophoresis. The sequence was read off the gel on the basis of cleavage patterns and size of the fragments. While the readout procedure provided only the positions of A, U, C, and G residues in the chain, additional information from tritium derivative analysis was utilized to define the positions of the modified nucleosides. The readout sequencing procedure was found to require less than 0.01 A260 unit of RNA and the analysis of the complete fragments about 6 A260 units. Interesting structural features of tRNA Leu UAG are (a) the location of unique, leucine tRNA iso-acceptor-specific sequences next to U-8, a constant nucleotide participating in synthetase recognition, (b) the occurrence of 1-methyladenosine in the T loop, a modification not present in the structurally related tRNA Leu m5CAA, and (c) the unusual presence of an unmodified uridine in the first position of the anticodon, which may be related to the unusual coding properties reported for this tRNA.
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PMID:Yeast tRNA Leu UAG. Purification, properties and determination of the nucleotide sequence by radioactive derivative methods. 37 75


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