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:3.1.26.9 (ribonuclease)
6,589 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Preparations of purified and disrupted suspensions of Coxiella burnetii are able to incorporate ribonucleotides into polymers in the presence of adenosine, guanosine, cytidine, and uridine triphosphates. Nucleotide incorporation requires the presence of all four ribonucleoside triphosphates. The reaction is enhanced by the addition of phosphoenolpyruvate and pyruvic kinase, and exogenous deoxyribonucleic acid, and is inhibited by deoxyribonuclease and actinomycin D. Incorporation is maximal between pH 7.0 and 8.0, and at 37 C. The synthesized polymer is relatively insensitive to deoxyribonuclease and is sensitive to ribonuclease and dilute alkaline hydrolysis. The data indicate the presence of an autonomous deoxyribonucleic acid-dependent ribonucleic acid polymerase in the rickettsial agent.
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PMID:Physiology of rickettsiae. VI. Host-independent synthesis of polyribonucleotides by Coxiella burnetii. 602 13

1. A ribonuclease has been partially purified from the cotyledons of germinating seed of Pisum arvense. 2. The enzyme degrades ribopolynucleotides to adenosine 3'-phosphate, guanosine 3'-phosphate and the cyclic nucleotides cytidine 2',3'-phosphate and uridine 2',3'-phosphate; no resistant ;core' remains. 3. The activity of RNA-degrading enzymes in the cotyledons increases to a maximum during the first 5 days of germination, passes through a minimum around the eighth day, and thereafter increases again. 4. Ion-exchange chromatography of methanol-soluble extracts of cotyledons revealed the presence, amongst other components, of the 2'-, 3'- and 5'-phosphates of cytidine and uridine, the 3'- and 5'-phosphates of adenosine, and guanosine 5'-phosphate. 5. Seed soaked in a solution containing [(32)P]orthophosphate gave a methanol-soluble fraction containing labelled nucleoside 5'-phosphates, but nucleoside 2'- and 3'-phosphates were not labelled. 6. It is believed that the nucleoside 2'- and 3'-phosphates arise by the action of ribonuclease on cotyledon RNA.
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PMID:The degradation of ribonucleic acid in the cotyledons of Pisum arvense. 603 62

Treponema pallidum (Nichols strain), extracted in medium containing Eagle minimal essential medium 50% fresh, heat-inactivated normal rabbit serum, and 1.0 mM dithiothreitol, was incubated under 3% oxygen in the presence of tritiated nucleic acid precursors. [8-3H]adenine was incorporated with high efficiency into trichloroacetic acid-insoluble material; 2'-deoxyadenosine and uridine were incorporated in lower quantities, and thymine and thymidine were not incorporated. Incorporation of [3H]adenine was inhibited by penicillin G, mitomycin C, actinomycin D, and erythromycin, but was not affected by cycloheximide. Partial purification of nucleic acids from T. pallidum incubated with [8-3H]adenine for 36 to 72 h and subsequent treatment with ribonuclease and deoxyribonuclease revealed that 15 to 20% of the trichloroacetic acid-precipitable counts were resistant to ribonuclease but susceptible to deoxyribonuclease. A simple assay was developed in which NaOH treatment was used to distinguish incorporation into ribonucleic acid and deoxyribonucleic acid. Both ribonucleic acid and deoxyribonucleic acid synthesis continued for 6 days of incubation under 3% O2, whereas incorporation was limited to the first day of incubation in samples incubated under aerobic or anaerobic conditions. T. pallidum thus appears to be capable of significant de novo deoxyribonucleic acid and ribonucleic acid synthesis under microaerobic conditions.
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PMID:Long-term incorporation of tritiated adenine into deoxyribonucleic acid and ribonucleic acid by Treponema pallidum (Nichols strain). 615 24

The synthesis of cytidine, uridine, guanosine, and adenosine 3'-(S-methyl phosphorothioates) by treatment of the 2',5'-di-O-(4-methoxytetrahydropyran-4-yl)ribonucleosides with 2-(methylthio 4H-1,3,2-benzodioxaphosphorin 2-oxide is described. These nucleotide analogues are stable compounds both in the solid state and the neutral aqueous solution. All four of these compounds are degraded by RNase T2 to the parent nucleotides and methanethiol. In addition, cytidine and uridine 3'-(S-methyl phosphorothioates) are substrates for bovine pancreatic ribonuclease and guanosine 3'-(S-methyl phosphorothioate) is a substrate for RNase T1 and RNase U1. When used in conjunction with a chromophore-producing reagent, nucleoside 3'-(S-methyl phosphorothioates) provide a means for direct kinetic measurement of ribonuclease activity over a wide pH range (pH 2-9). The reactivities of these substrates with ribonucleases are compared to the reactivities of other synthetic substrates as well as a number of natural substrates. The utility of ribonucleoside 3'-(S-methyl phosphorothioates) as substrates for the assay of ribonucleases is discussed.
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PMID:Synthesis of nucleoside 3'-(S-alkyl phosphorothioates) and their use as substrates for nucleases. 627 Nov 88

Cells of intraperitoneally transplanted murine leukaemias and sarcomas (L-1210, EL-4, MC-11 and SA-1), were found to be toxic for target cells usually employed for assaying NK cells (K-562, EL-4, YAC-1). The 3H-uridine-ribonuclease method used in our study, in contrast to the 51Cr assay, revealed not only cytotoxicity but also reversible damage to target cell membrane (membrane toxicity). This damage became irreversible if target cells had been pretreated with actinomycin D. To exclude the possible role of an admixture of NK, macrophages and T killer cells, contaminants were removed from suspensions of peritoneal tumour cells from syngeneic mice by adherence to plastic surfaces and separation on Hypaque-Ficoll, and from tumour cells grown in vivo or in vitro and then maintained in allogeneic animals by additional treatment with anti-H-2 sera and complement. The toxic effect depended directly on the dosage of tumour cells. Unlabelled target cells inhibited tumour cell toxicity. The medium used for incubating tumour cells was not toxic for target cells.
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PMID:Tumour cell toxicity for the targets of natural killer cells. 664 10

The endoribonuclease VI from Artemia larvae is non-competitively inhibited by cytidine 2'-phosphate with a Ki ca 1 microM. Neither of the cytidine monophosphates isomers with the phosphate group in the 3' or 5' position nor the cyclic 2':3' phosphate are inhibitors at concentrations up to 100 microM. Adenosine, guanosine and uridine 2' or 3' phosphates are also ineffective in this range of concentrations. Certain polyribonucleotides are potent competitive inhibitors of the ribonuclease activity.
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PMID:Inhibition of endoribonuclease VI from Artemia larvae by cytidine 2'-phosphate. 673 17

The complete nucleotide sequences of human placenta, human liver, and bovine liver tRNAAsn have been determined. A comparison of these tRNA structures with the previously reported nucleotide sequences of rat liver and Walker 256 carcinosarcoma tRNAAns reveals that the primary nucleotide sequences of the major species of mammalian cytoplasmic tRNAasn are conserved in higher eucaryotes. The complete nucleotide sequence of these tRNAs is: pG-U-C-U-C-U-G-U-m1G-m2G-C-G-C-A-A-D-C-G-G-D-X-A-G-C-G-C-m2(2)G-psi-psi-C-G-G-C-U-Q(G)-U-U-t6A-A-C-C-G-A-A-A-G-m7G-D-U-G-G-U-G-G-Z-psi-C-G-m1A-G-C-C-C-A-C-C-C-A-G-G-G-A-C-G-C-C-AOH where X is 3-(3-amino-3-carboxyl-n-propyl)uridine, Q is 7-(4,5-cis-dihydroxyl-1-cyclopenten-3-yl-aminomethyl)-7-deazaguanosine, Z is an unknown modified nucleotide, and Q(G) represents the replacement of Q nucleoside by G nucleoside in Walker 256 carcinosarcoma tRNAAsn. These primary structures were determined by combined use of the 3H- and 32P-post-labeling techniques. Sequences were compared by tritium nucleoside trialcohol analysis, completed RNAase T1 digestion followed by 3H-labeled fingerprinting on polyethylenimine-impregnated cellulose by two-dimensional thin-layer chromatography (TLC), and polyacrylamide gel electrophoresis of either 5'-32P- and/or 3'-[32P]pCp-labeled tRNA after partial ribonuclease digestions.
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PMID:Structural comparison of human, bovine, rat, and Walker 256 carcinosarcoma asparaginyl-tRNA. 678 75

RNA and protein interaction in the structure of influenza virus ribonucleoprotein (RNP) was studied by ultraviolet (UV) irradiation. After UV-irradiation of virion RNP for 1 hour only 6% of 3H-uridine-labeled RNA was found to go into the aqueous phase upon phenol-detergent extraction. Pretreatment of RNP with small doses of pancreatic RNase before RNA extraction slightly increased (up to 18%) the amount of RNA going into the aqueous phase. About 90% RNA was found after extraction in the aqueous phase in the nonirradiated material. As a result of UV-irradiation of RNP, RNA in RNP became more resistant to RNase: the residual acid-insoluble radioactivity was 21% whereas with nonirradiated RNP it was 3.2%. The results of the analysis of RNP labeled for protein in polyacrylamide gel and SDS-sucrose gradient after UV-irradiation and ribonuclease treatment indicate the formation of UV-induced linkages between RNA and NP protein.
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PMID:[RNA-protein interactions in influenza virus A ribonucleoprotein detected by UV radiation]. 733 92

This study investigates the effects of hypoxia and of cobalt on erythropoietin (EPO) gene expression in hepatocytes in vivo and in vitro in neonatal, juvenile, and adult rats. With the use of the ribonuclease protection assay to quantify RNA, both hypoxia (0.1% CO or 9% O2) and cobalt (60 mg/kg) elicit production of increased amounts of EPO mRNA in neonatal and juvenile rat liver in vivo. In vitro hepatocyte EPO gene expression could be reproducibly stimulated by hypoxia (3% O2) but not by cobaltous chloride (50-150 microM) within 2-20 h. Conversely, cobalt substantially attenuated the rise of EPO mRNA levels in response to hypoxia. This inhibitory effect of cobalt was mimicked by zinc but not by other metals. CO attenuated the rise of EPO mRNA levels in vitro in response to hypoxia; this inhibitory effect coincided with an inhibition of total RNA synthesis as determined by [3H]uridine incorporation. The lack of specific inhibitory effects of CO and of specific stimulatory effects of cobalt on hepatocyte EPO gene expression in vitro suggests that a specific heme oxygen sensor may be less important than in hepatoma cells.
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PMID:Cobalt exerts opposite effects on erythropoietin gene expression in rat hepatocytes in vivo and in vitro. 750 28

Ribonucleases catalyze the hydrolysis of the P-O5' bond in RNA. This reaction occurs in two steps: transphosphorylation of RNA to a 2',3'-cyclic phosphodiester intermediate and hydrolysis of this intermediate to a 3'-phosphomonoester. 31P NMR spectroscopy was used to monitor the accumulation of the 2',3'-cyclic phosphodiester intermediate during the transphosphorylation and hydrolysis reactions catalyzed by various ribonucleases and by small molecules. The intermediate was found to accumulate during catalysis by monomeric bovine pancreatic ribonuclease A (RNase A), a dimer and a trimer of RNase A, bovine seminal ribonuclease, RNase T1, barnase, and RNase 1. These enzymes, which are of widely disparate phylogenetic origin, released rather than hydrolyzed most of the intermediate formed transphosphorylation of RNA. In contrast, the intermediate did not accumulate during catalysis by hydroxide ion or imidazole buffer. In the presence of these small molecules, hydrolysis is faster than transphosphorylation. A trapping experiment was used to assess the throughput of the reaction catalyzed by RNase A. [5,6-3H]Uridylyl-(3'-->5')adenosine was incubated with RNase A in the presence of excess unlabeled uridine 2',3'-cyclic phosphodiester, which dilutes the specific radioactivity of any released cyclic intermediate. Only 0.1% of the RNA substrate was found to be both transphosphorylated and hydrolyzed without dissociating from the enzyme. These results suggest that ribonucleases have evolved primarily to catalyze RNA transphosphorylation and not RNA hydrolysis.
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PMID:Energetics of catalysis by ribonucleases: fate of the 2',3'-cyclic phosphodiester intermediate. 800 6


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