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:3.1.13.1 (exoribonuclease)
732 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The infectivity of replicative form RNA (RF-RNA) isolated from poliovirus-infected HeLa cells is completely resistant to the action of T-1 RNase but decreases after exposure to RNase A in the presence of 0.3 M NaCl. Under these conditions neither enzyme produces single-stranded nicks in RF-RNA. Three endonuclease-free exonuleases (RNase II, polynucleotide phosphorylase and spleen phosphodiesterase) rapidly destroy the infectivity of single-stranded RNA, but do not alter the infectivity of RF-RNA. It is concluded that RF-RNA does not contain single-stranded ends essential for infectivity. Indirect evidence suggests that all or most of the poly A region at the 3' end of the plus strand of infectious RF-RNA is base-paired to a poly U region at the 5 end of the minus strand.
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PMID:Poliovirus-induced infectious double-stranded RNA: Effect of RNA-degrading enzymes. 16 28

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

The acid-soluble ribonucleic acid degradation products formed by Escherichia coli cells starved for a carbon source have been identified. They comprise oligonucleotides, nucleoside diphosphates, 5'- and 3'-nucleoside monophosphates, nucleosides, and free bases. The majority of these products are excreted phates, nucleosides, and free bases. The majority of these products are excreted into the medium, and only small and constant amounts are kept in the pool. During carbon starvation at elevated temperatures, mutants deficient in ribonuclease I do not form oligonucleotides and 3'-nucleoside monophosphates, and mutants that contain a modified form of polynucleotide phosphorylase do not accumulate nucleoside diphosphates. 5'-Nucleoside monophosphates do accumulate, however, in a mutant containing thermoabile ribonuclease II, under conditions where more than 95% of all enzyme activity had been destroyed. The data presented confirm the participation of ribonuclease I and polynucleotide phosphorylase in the final steps of ribonucleic acid degradation and indicate that an exonuclease forming 5'-nucleoside monophosphates is also involved.
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PMID:Accumulation of nucleotides by starved Escherichia coli cells as a probe for the involvement of ribonucleases in ribonucleic acid degradation. 32 Jan 88

The disappearance of ribosomes in Escherichia coli cells starved for a carbon source was studied. We used a series of mutants, some of them lacking in ribonuclease I(RNase I, EC 2.7.7.17), and other containing various combinations of modified polynucleotide phosphorylase (PNPase, EC 2.7.7.8) and modified ribonuclease II (RNase II, EC 3.1.4.1). RNA was prepared from the starved mutant cells and separated on polyacrylamide gels. The results obtained indicate that 23 S RNA degradation is similar in all strains that lack RNase I, and is slightly increased in the strain that contains this enzyme. The extent of 16 S RNA degradation is identical in all strains tested. RNA species in the size of 4 S and smaller accumulate in mutants containing modified forms of PNPase and RNase II. The appearance of an RNA species 10% smaller than 16 S RNA (d16 S RNA) was observed in all strains that contain unmodified RNase II. Analysis of ribosomes and polysomes and their RNA content indicated that polysomes are converted to monosomes and these, in turn, to ribosomal subunits. No RNA degradation products were found in polysomes, 70 S, OR 50 C particle; 30 S subunits contained 16 S RNA as well as the d16 S RNA species. Subunits are degraded to a similar extent in all strains lacking RNase I, and at a slightly faster rate in the strain that contains RNase I. The RNA to protein ratio in subunits prepared from starved cells is similar to that of unstarved cultures. Very little degradation of ribosomal proteins occurs in these mutants during carbon starvation. The proteins released from degraded ribosomes are found in the fast sedimenting (20,000 times g) pellet. Cell viability studies indicated a direct correlation between the capacity of the mutants to recovery from starvation and their capacity to degrade RNA. Thus a biological necessity for degradation of ribosomes during starvation is implied. Based on these data we propose that the endonucleolytic degradation of ribosomal RNA is the primary event in starvation degradation. It takes place in ribosomal subunits, which fall apart after the endonucleoltic attack. The RNA pieces produced by this cleavage are degraded to nucleotide by RNase II and PNPase. The ribosomal proteins attach to the cell membrane.
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PMID:The fate of ribosomes in Escherichia coli cells starved for a carbon source. 108 66

Decay of pre-existing ribonucleic acid was studied in Escherichia coli cells subjected to high temperature or to starvation for nitrogen, phosphate, amino acids, or a carbon source. In these studies a series of mutants affected in ribonucleic I(RNase I, EC 3.1.4.22) polynucleotide phosphorylase (EC 2.7.7.8) or ribonuclease II (RNase II, EC 3.1.4.23) were used. Degradation of total RNA and the disappearance of 23 S and 16 S rRNA were followed. The results obtained indicated that, by and large, decay of 23 S and 16 S RNA parallels that of total RNA. Decay of RNA depended on the nuclease content of the cells as well as on the treatment of applied. It was most pronounced during carbon starvation and least in cells deprived of phosphate ions. It was most effective in strains containing all three nucleases and least in the strain defective in all three. The exonucleases polynucleotide phosphorylase and RNase II did not seem to affect the extent of 23 S and 16 S RNA disappearance. Strains with modified exonucleases did accumulate low molecular weight RNA species during treatments which induced considerable degradation of 23 S and 16 S RNA. Based on the above date and previous observations, we suggest that during various starvations a similar mechanism is operative. The 23 S and 16 S RNAs are degraded endonucleolytically, and this is the rate-limiting step during starvation. The exonucleases polynucleotide phosphorylase and RNase II seem to participate primarily in the decay of the low molecular weight RNA species formed by the endonuclease(s), not as yet identified.
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PMID:Decay of ribosomal ribonucleic acid in Escherichia coli cells starved for various nutrients. 109 48

In a mutant strain defective in polynucleotide phosphorylase, under conditions where the enzyme becomes limiting, it is possible to demonstrate that chemical as well as functional half lives of mRNA become longer if the strain is also missing ribonuclease II. These results allow to unify in a simple model a variety of observations about turnover of RNA in a variety of bacteria.
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PMID:Polynucleotide phosphorylase can participate in decay of mRNA in Escherichia coli in the absence of ribonuclease II. 110 47

RNase PH is a Pi-dependent exoribonuclease that can act at the 3' terminus of tRNA precursors in vitro. To obtain information about the function of this enzyme in vivo, the Escherichia coli rph gene encoding RNase PH was interrupted with either a kanamycin resistance or a chloramphenicol resistance cassette and transferred to the chromosome of a variety of RNase-resistant strains. Inactivation of the chromosomal copy of rph eliminated RNase PH activity from extracts and also slowed the growth of many of the strains, particularly ones that already were deficient in RNase T or polynucleotide phosphorylase. Introduction of the rph mutation into a strain already lacking RNases I, II, D, BN, and T resulted in inviability. The rph mutation also had dramatic effects on tRNA metabolism. Using an in vivo suppressor assay we found that elimination of RNase PH greatly decreased the level of su3+ activity in cells deficient in certain of the other RNases. Moreover, in an in vitro tRNA processing system the defect caused by elimination of RNase PH was shown to be the accumulation of a precursor that contained 4-6 additional 3' nucleotides following the -CCA sequence. These data indicate that RNase PH can be an essential enzyme for the processing of tRNA precursors.
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PMID:RNase PH is essential for tRNA processing and viability in RNase-deficient Escherichia coli cells. 164 89

The Escherichia coli glyA structural gene is followed by two REP sequences and a rho-independent transcription terminator. These sequences are essential for maintaining glyA mRNA stability and gene expression by blocking the 3' to 5' exonucleolytic activities of polynucleotide phosphorylase and ribonuclease II. The results support the model of cooperative endonucleolytic and 3' to 5' exonucleolytic activities in mRNA decay.
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PMID:Escherichia coli glyA mRNA decay: the role of 3' secondary structure and the effects of the pnp and rnb mutations. 169 34

The rapid synthesis and breakdown of mRNA in prokaryotes can impose a significant energy drain on these cells. Previous in vivo studies [Duffy, J. J., Chaney, S. G. & Boyer, P. D. (1972) J. Mol. Biol. 64, 565-579; Chaney, S. G. & Boyer, P. D. (1972) J. Mol. Biol. 64, 581-591] indicated that while RNA turnover in Escherichia coli was hydrolytic, it was nonhydrolytic in Bacillus subtilis. Here we provide an explanation for these observations based on enzymatic analysis of extracts of these two organisms. RNA degradation to the mononucleotide level in E. coli extracts is due solely to two active ribonucleases, RNase II and polynucleotide phosphorylase, which act hydrolytically and phosphorolytically, respectively. RNase II activity represents close to 90% of the total activity of the extract, as expected for predominantly hydrolytic degradation in this organism. In contrast, RNase II is absent from B. subtilis extracts, and the primary mode of RNA degradation is phosphorolytic, employing the Bacillus equivalent of polynucleotide phosphorylase and releases nucleoside diphosphates as products. A low level of a Mn2(+)-stimulated, hydrolytic ribonuclease is also detectable in B. subtilis extracts. Overall, E. coli and B. subtilis extracts differ by about 20- to 100-fold, depending on the substrate, in their relative use of hydrolytic and phosphorolytic routes of RNA degradation. The relation of the mode of mRNA degradation to the environment of the cell is discussed.
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PMID:Enzymatic basis for hydrolytic versus phosphorolytic mRNA degradation in Escherichia coli and Bacillus subtilis. 170 36

Escherichia coli RNase PH is a phosphate-dependent exoribonuclease that has been implicated in the 3' processing of tRNA precursors. It degrades RNA chains in a phosphorolytic manner releasing nucleoside diphosphates as products. Here we show that RNase PH also catalyzes a synthetic reaction, the addition of nucleotides to the 3' termini of RNA molecules. The synthetic activity co-purifies with RNase PH throughout an extensive enrichment indicating that it is due to the same enzyme. The synthetic activity can incorporate all nucleoside diphosphates, but not triphosphates, and is strongly inhibited by Pi, but not PPi. Various RNA molecules stimulate nucleotide incorporation, and with tRNA the 3' end of the molecule serves a primer function. RNA chains as long as 40 residues can be synthesized in this system. As with polynucleotide phosphorylase, the synthetic activity of RNase PH apparently represents the reversal of the degradative reaction.
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PMID:RNase PH catalyzes a synthetic reaction, the addition of nucleotides to the 3' end of RNA. 170 83


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