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)

Ribonucleases O and Q, the two putative nucleolytic activities which we detected previously in the crude extract from a thermosensitive ribonuclease P mutant (TS241) of Escherichia coli and which were shown to function in the processing of tRNA precursors in vitro, were partially purified from the 1000000 x g supernatant fraction of E. coli Q13. In the course of purification of these enzymes, the total RNAs synthesized in the thermosensitive mutant at the restrictive temperature were used as the substrates and the activities were identified from disappearance or alteration of specific tRNA precursor molecules in polyacrylamide gel electrophoresis. The purified ribonuclease O preparation cleaved specifically the multimeric tRNA precursors at the spacer regions. The purified ribonuclease Q preparation removed, in accordance with the definition of this enzyme, extra nucleotides from the 3'-terminal ends of monomeric tRNA precursors. Some properties of these two nucleases were investigated. In addition to these nucleases, another exonuclease (tentatively designated ribonuclease Y) and ribonuclease P, a well-characterized endonuclease, were also purified. The sequential mode of the processing of tRNA precursors, originally observed in the cleavage reactions with the crude extracts in vitro, was supported by studies with the purified enzyme preparations.
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PMID:Specific ribonucleases involved in processing of tRNA precursors of Escherichia coli. Partial purification and some properties. 35 May 82

Two species of 32P-labelled leucine tRNA were highly purified from Candida (Torulopsis) utilis by successive column chromatographies. The purified major species of leucine tRNA 1 was completely digested with ribonuclease T1 [EC 3.1.4.8] and with pancreatic ribonuclease A [EC 3.1.4.22]. The resulting fragments were fractionated, and their nucleotide sequences were determined according to Barrell (1). The results of analyses of the two ribonuclease digests were consistent with each other, and indicated that this tRNA is composed of 85 nucleotide residues, including 14 modified nucleotides. A tentative total sequence has been derived on the basis of several features in the cloverleaf structure for tRNA.
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PMID:Nucleotide sequence of leucine transfer RNA 1 from Candida (Torulopsis) utilis. 35 Aug 63

When treated at pH less than 4.5, yeast nuclei or chromatin lose endogenous RNA synthetic activity. This activity is regained by addition of exogenous RNA polymerases. The specificity of transcription in this system by homologous RNA polymerases I and III has been investigated by gel electrophoresis, hybridization analysis, and RNase T1 mapping. Exogenous RNA polymerase I selectively transcribes rRNA genes. The transcription of these genes by polymerase I is 30- and 8-fold more selective than RNA polymerase III and Escherichia coli polymerase holoenzyme, respectively. Exogenous RNA polymerase III synthesized RNAs similar in size to authentic 5 S RNA, 4.5 S pre-tRNA, and 4 S tRNA. Eleven per cent of this RNA is 5 S RNA as determined by hybridization. Neither polymerase I nor E. coli polymerase synthesizes detectable quantities of RNA in this size range. AT1 ribonuclease digestion of 5 S RNA synthesized by exogenous RNA polymerase III acting on acid-treated chromatin gives a fragment pattern corresponding to that of 5 S RNA. Thus, RNA polymerase III transcribes the entire 5 S gene in this system.
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PMID:Specific gene transcription in yeast nuclei and chromatin by added homologous RNA polymerases I and II. 36 64

Two dimensional PEI-cellulose thin layer chromatography can resolve sequentially degraded oligonucleotide fragments of tRNA. This technique entails the sequential degradation of the oligonucleotide with snake venom phosphodiesterase in the presence of bacterial alkaline phosphatase, and periodate oxidation followed by tritiated sodium borohydride reduction of the 3' terminal nucleoside. Subsequently the tritiated oligonucleotide fragments were resolved by two dimensional PEI-cellulose TLC. The results of these experiments indicate that, in some cases, the complete nucleotide sequence of a large oligonucleotide fragment may be determined by interpretation of the observed mobility shifts, thereby eliminiating the need for additional analysis of the oligonucleotide. In addition, the use of two-dimensional rather than one-dimensional resolution of the tritium labeled fragments allows for a complete separation of any interfering background spots from the sequentially degraded oligonucleotides. This procedure was applied to the complete nucleotide sequence analysis of several ribonuclease T1Val and ribonuclease A digestion products from human placenta tRNA.
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PMID:A two-dimensional thin layer chromatographic procedure for the sequential analysis of oligonucleotides employing tritium post-labeling. 41 70

The early stages of thermal unfolding of the tertiary structure of yeast tRNAPhe have been followed, in the presence and absence of Mg2+, by measuring changes in the chemical accessibility of the bases uracil and guanine. The reagent used in these studies is 1-cyclohexyl 3-[2-morpholino(4)-ethyl]carbodiimide methotosylate. 32P-labelled tRNA was used so that the points of modification could be examined with ribonuclease digestion and established fingerprinting techniques. Two regions of protection of Mg2+ have been found. One is within the oligonucleotide U8-A-m2G10 and the other is in the vicinity of residue U-59. The tertiary interactions and the D stem are the most readily melted parts of the teritary structure. In the absence of Mg2+ the region of U-59 is the first part of the tertiary structure to become accessible to the reagent. This is closely followed by the opening up of the 'wobble' G-U base pair in the aminoacyl stem. Most of the triple interactions in the augmented D helix are also disrupted early in the melting. The region of intricate interactions between the invariant G-G part of the D loop and the T-psi-C-G loop contains the most stable set of tertitary structure interactions.
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PMID:Initial stages of the thermal unfolding of yeast phenylalanine transfer RNA as studied by chemical modification: the effect of magnesium. 41 74

T1 ribonuclease digestion of yeast tRNASer in the presence of seryl tRNA synthetase was used for monitoring the relationship between the substrate binding sites on the synthetase. It was found that (a) ATP displaces the tRNA from the synthetase with an effector affinity constant corresponding to the Km for ATP of 10 micron; (b) AMP and a number of nucleoside triphosphates, while influencing the rate of aminoacylation, do not displace the tRNA from the enzyme; (c) ADP and PPi inhibit the aminoacylation and the binding of tRNASer; (d) adenylyl diphosphonate is bound to the synthetase and lowers the protection of the tRNA against the nuclease attack in a similar way as does ATP; (e) interactions between the sites of L-serine and tRNASer could only be shown when both sites for serine were saturated and, in addition, the ATP analog or ADP was present. It is concluded that in seryl tRNA synthetase binding sites for ATP interact with the ones for tRNA as well as with the ones for serine. These findings contribute to the understanding of the mechanism of aminoacylation.
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PMID:Yeast seryl tRNA synthetase: interactions between the ATP binding site and the sites for tRNASer and L-serine. 41 97

The tRNA nucleotidyltransferase activity (3H-CMP incorporation into 3'-terminus of tRNApC) in cytoplasmic fractions of various types of cells such as Ehrlich ascites tumor cells, mouse liver and spleen cells, rat spleen, lymph node, and macrophages cells was found to be dependent on the concentrations of nucleoside 5'-triphosphates (ATP, GTP, UTP, dATP, dGTP, dCTP, and/or dTTP). The purified tRNA nucleotidyltransferase did not show such dependency. The dependency of the enzyme activity on nucleoside 5'triphosphates in the crude cytoplasmic fractions was possibly due to the presence of inhibitors which interfere with the repair system of defective 3'-termini of tRNA. Two kinds of inhibitors were distinguishable in the cytoplasmic fractions. One was unstable on heat treatment at 55 decrees C and showed ribonuclease activity for the tRNA 3'-terminus. The other which lacked ribonuclease activity was rather stable to the heat treatment and inhibited purified tRNA nucleotidyltransferase. The actions of both inhibitors were suppressed by nucleoside 5'-triphosphates.
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PMID:Effect of nucleoside 5'-triphosphates on tRNA nucleotidyltransferase activity in cytoplasmic fractions of various types of mammalian cells. 42 63

Cell-free protein synthesizing systems were prepared from the livers of chick embryos at selected ages and the characteristics of individual fractions were compared. While polysomes showed decreasing size with older embryos, isolated polysomes did not differ significantly in amino acid incorporating activity when assayed with standard cell sap. When assayed with standard polysomes, cell sap activity decreased with increasing developmental age whether incorporation was measured using (3H)lysine, (3H)leucine, or [3H]aminoacyl-tRNA. Free amino acid concentrations in the cell sap showed reproducidble independent variation during development which was taken into consideration in calculating net amino acid incorporation. A larger increase in ribonuclease activity was observed during development; however, nuclease inhibitor activity was absent before day 15 but increased thereafter. Aminoacyl-tRNA sythetase activity did not vary significantly. It is proposed that the observed changes in the rate of cell-free protein synthesis result not only from increasing ribonuclease activity with increasing developmental age but also from changes in the activity of other soluble factors.
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PMID:Polymorphism in fowl serum albumin. VI. Changes in in vitro protein synthesizing activity in developing embryonic fowl liver. 46 Jan 76

1. Vitamin A deficiency led to an increase in the oligonucleotide fraction of testes and intestinal mucosa of rats at the expense of high-molecular-weight RNA and 4S RNA, but no such changes were observed in the liver. Retinyl acetate supplementation reversed these effects in both tissues, whereas retinoic acid supplementation was almost equally effective in the mucosa but virtually ineffective in the testes. The ribonuclease activities of all the tissues remained unaffected by the above treatments. 2. The effect of vitamin A deprivation on the acceptor activity of the tRNA of the testes and intestinal mucosa was more pronounced than on the liver tRNA. The testes and mucosal tRNA of the retinoic acid-supplemented rats showed significantly lower charging capacity as compared with the retinyl acetate-supplemented ones. Here also no significant effect was observed on the liver tRNA. 3. Vitamin A deficiency caused a decrease in the percentage of poly(A) in RNA of the mucosa and testes, but not in the liver RNA. The poly(A) contents of both tissues were brought to normal by retinyl acetate supplementation; treatment with retinoic acid led to an appreciable increase in poly(A) in the mucosa, but considerably less increase in poly(A) in the testes. 4. The incorporation of H332PO4 into the rRNA and tRNA of the testes was lowered by vitamin A deficiency, but no such effects was observed in the liver RNA.
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PMID:Effect of vitamin A nutritional status on the ribonucleic acids of liver, intestinal mucosa and testes of rats. 59 29

tRNA(guanine-1-)-methyltransferase (EC 2.1.1.31) and tRNA(N2-guanine)-methyltransferase I (EC 2.1.1.32) were isolated from rat liver. The (guanine-1-)-methyltransferase preparation is 6800-fold purified and is free from contaminating methyltransferases or ribonuclease. The molecular weight of (guanine-1-)-methyltransferase is 83 000. Of seven purified Escherichia coli tRNAs examined, only tRNAMetf was utilized as substrate by (guanine-1-)-methyltransferase. The methylation of tRNAMetf is maximally stimulated by 40 mM putrescine with a pH optimum of 8.0. Using E. coli K-12 tRNA, the Km for S-adenosylmethionine is 3 micrometer and Ki for S-adenosylhomocysteine is 0.11 micrometer for (guanine-1-)-methyltransferase. (N2-Guanine-)-methyltransferase is 6200-fold purified and is also free of interfering enzymes. It has a molecular weight of 69 000. E. coli tRNAPhe, tRNAVal and tRNAArg are substrates for this enzyme which introduces a methyl at the 2-amino group of the guanine at position 10 from the 5'-terminus of these tRNAs. The methylation of tRNAPhe is maximally stimulated by 100 micrometer spermidine with a pH optimum of 8.0. (N2-Guanine-)-methyltransferase has a Km for S-adenosylmethionine of 2 micrometer and a Ki for S-adenosylhomocysteine of 23 micrometer with E. coli K-12 tRNA as methyl acceptor.
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PMID:Purification and characterization of two tRNA-(guanine)-methyltransferases from rat liver. 62 73


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