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)

Escherichia coli RNase D and RNase II have been purified to homogeneity and compared for their ability to remove extra nucleotides following the -C-C-A sequence in tRNA precursors. RNase D and RNase II are single-chain proteins with molecular weights of 38,000 and 78,000, respectively. Both enzymes require a divalent cation for activity on tRNA precursors, but, in addition, RNase II is stimulated by monovalent cations. RNase D specifically removes mononucleotide residues from a mixture of tRNA precursors to generate amino acid acceptor activity for essentially all amino acids. Although RNase II can also remove precursor-specific residues, no amino acid acceptor activity is recovered. Similarly, RNase D action on the E. coli tRNATyr precursor is limited, whereas RNase II causes extensive degradation. In contrast to the processive mode of hydrolysis by RNase II, RNase D removes nucleotides randomly and slows down greatly at the -C-C-A sequence, thereby allowing the tRNA to be aminoacylated and protected from further degradation. These results suggest that RNase D is the 3'-processing nuclease in vivo and that RNase II is a nonspecific degradative enzyme. The importance of RNA conformation for correct processing is also discussed.
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PMID:Apparent involvement of ribonuclease D in the 3' processing of tRNA precursors. 615 5

In 1974 we introduced the quail oviduct system to molecular gerontology as a model for investigating age-dependent gene realization at the molecular level. During ageing the amounts of synthesized ovalbumin and avidin, the two major oviduct proteins, decrease to reach almost 0-values. Soon it emerged that the reasons for the reduced ovalbumin and avidin syntheses were not only on the transcriptional but in addition on the posttranscriptional level. It was found that the observed reduced capacity for protein biosynthesis was an age-correlated impairment of those enzyme systems which are involved in the processing of hnRNA to mRNA and in the transport of mRNA from nucleus to cytoplasm. After having firstly discovered and purified some key enzymes of mRNA processing ( endoribonucleases IV, V and VII; U1- snRNP -associated endoribonuclease; poly(A)-specific exoribonuclease ), and secondly studied in detail the enzymically controlled nucleocytoplasmic mRNA transport system, we observed that polyadenylation and perhaps also splicing of hnRNA (two processes in posttranscriptional modification of mRNA) are impaired during ageing. Pronounced changes occur especially at the level of polyadenylation of hnRNA; analytic and enzymic studies revealed that, in parallel with ageing, poly(A) catabolism increases although poly(A) anabolism remains unchanged. The consequences of this change are: reduced stability of mRNA, probably reduced splicing efficiency, reduced binding of mRNA to the inner nuclear membrane or lamina, and reduced nucleocytoplasmic transport of mRNA. The data suggest that changes at the posttranscriptional level are as important in ageing as changes in transcription, and they may explain the observed, age-dependent reduction of the amount of functional mRNA in the cytoplasm.
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PMID:[Age-dependent gene induction in the quail oviduct. Role of post-transcriptional changes in the aging process]. 620 35

For the simultaneous determining of several enzymes of nucleic acid metabolism during polynucleotide phosphorylase isolation TLC was used. It was found that using TLC one can simultaneously detect six and more enzymes, e. g. polynucleotide phosphorylase, 5'-nucleotidase, exoribonuclease together with nucleosidediphosphatase, desaminase etc. The method is simple and accessible.
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PMID:[Use of a TLC method for the simultaneous determination of an enzyme complex of nucleic acid metabolism during the isolation of polynucleotide phosphorylase]. 620 91

A multiple mutant strain of Escherichia coli containing mutations affecting the exoribonucleases, RNase II, RNase D, and RNase BN, and also the endonuclease, RNase I, was constructed by P1-mediated transduction. Extracts of the mutant strain were lacking the aforementioned RNase activities. The multiple mutant displayed normal growth in both rich and minimal media at a variety of temperatures, recovered from starvation essentially as the wild-type parent, and could support the growth of a variety of bacteriophages. In addition, RNA synthesis was normal and no precursor RNA accumulation was observed. The properties of the mutant strain indicate that the three exoribonucleases are not essential for the viability of E. coli. The implications of these findings to our understanding of RNA processing and degradation are discussed.
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PMID:A multiple mutant of Escherichia coli lacking the exoribonucleases RNase II, RNase D, and RNase BN. 620 70

A single-strand-specific, nucleolar exoribonuclease from Ehrlich ascites tumor cells has been isolated and purified free from other nucleases. The exonuclease degraded single-stranded RNA processively from either a 5'-hydroxyl or a 5'-phosphorylated end and released 5'-mononucleotides. The enzyme digested single-strand poly(C), poly(U), and poly(A) equally well but did not degrade duplex poly(C).poly(I) or poly(A).poly(U). Less than 0.2% of duplex DNA or 1.5% of heat-denatured DNA was degraded under the conditions which resulted in greater than 26% degradation of RNA. The ribonuclease required Mg2+ (0.2 mM) for optimum activity and was inhibited by ethylenediaminetetraacetic acid but not by human placental RNase inhibitor. The native enzyme had a Stokes radius of 42 A and a sedimentation coefficient (S20,w) of 4.3 S. From these values, an apparent molecular weight of 76 000 was derived by using the Svedberg equation. The localization and unique mode of degradation suggest a role for the 5'----3' exoribonuclease in ribosomal RNA processing.
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PMID:Isolation and properties of a single-strand 5'----3' exoribonuclease from Ehrlich ascites tumor cell nucleoli. 620 56

An exoribonuclease producing 5'-mononucleotides has been purified from ribosomes of Saccharomyces cerevisiae. The enzyme has a broad pH optimum around 8.0, requires divalent cation, and is stimulated by monovalent cation with the cation and degree of stimulation being dependent on the substrate used. With either poly(A) or rRNA as substrate, the enzyme has a processive mode of hydrolysis. The oligonucleotides, (pA)3-5, are hydrolyzed by the enzyme, and the hydrolysis is dependent on a 5'-phosphate end group. Phosphorylation of the 3' end has little effect on the rate of hydrolysis. With [3H]poly(A) or [3H]rRNA, labeled differentially at the 5' termini, a more rapid release of 5'-terminal label can be shown, providing evidence that the enzyme hydrolyzes in a 5' leads to 3' direction. Further evidence for a 5' leads to 3' mode of hydrolysis is provided by a study of the products of the hydrolysis of [3H](pA)5 labeled at the 5' termini with 32P. No 32P label is found in (pA)2 which accumulates as an intermediate.
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PMID:Purification and characterization of a Saccharomyces cerevisiae exoribonuclease which yields 5'-mononucleotides by a 5' leads to 3' mode of hydrolysis. 624 7

An exoribonuclease from calf thymus which specifically cleaves poly(A) in the single- or in the double-stranded form has been isolated and purified to homogeneity. The enzyme has a molecular weight of about 80,000 as estimated by gel filtration, and consists of two subunits with molecular weights of 58,000 and 31,000 as analyzed by sodium dodecyl sulfate-gel electrophoresis. For optimal activity, the poly(A)-specific exoribonuclease requires divalent cations, alkaline pH, and 39 degrees C. The enzyme is inhibited at 0.2 ionic strength and is sensitive to reagents for thiol groups. The only product formed by the action of the enzyme is 5'-AMP. It is suggested that this enzyme plays a role in the degradation of the poly(A) sequence of mRNA in the nucleus.
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PMID:Purification and characterization of a poly(A)-specific exoribonuclease from calf thymus. 624 77

The complexes between a proteinaceous inhibitor and neutral ribonuclease II (EC 3.127.5) purified from low ionic strength extracts of normal and dystrophic mouse muscle are essentially indistinguishable in (a) purification behavior, (b) apparent molecular weights of approximately 50 000, (c) thermal denaturation (50% loss of activity in 5 min at 73.5 degrees C), (d) isoelectric points (pH 4.8), and (e) procedures for reversible resolution into free inhibitor and free RNase II. The free RNase II species are also similar whether obtained by resolution of the purified complexes or by direct isolation of free enzyme from dystrophic muscle. All have apparent molecular weights of 11 500 compared with 13 700 for bovine pancreatic RNase A; all retain 80% of activity after 5 min at 95 degrees C. The active RNase II prepared directly from muscle, by resolution of inhibitor complexes or by organic mercurial treatment of the inhibitor complexes, all have identical pH-activity profiles in 200 mM KC1 with an optimum near pH 7.0. In comparison RNase A has an optimum pH near 7.5 and its activity decreases more rapidly as KC1 concentration is increased above 50 mM KC1. RNase II inhibitor obtained by resolution of the purified complexes or by direct isolation in the free form from normal muscle extracts has an apparent molecular weight of 42 000 and is very sensitive to heat; it loses all activity at 40 degrees C in 5 min. These studies (a) provide methods for obtaining useful amounts of the components of the neutral RNase II - inhibitor system from muscle, (b) provide the first method reported for the reversible resolution of RNase II - inhibitor complexes, (c) fail to show any distinct difference between corresponding components of the system from normal and dystrophic mice, (d) establish interesting differences between the apparently homologous enzymes, murine muscle neutral RNase II, and bovine pancreatic RNase A, and (e) provide a substantially lower molecular weight estimate for RNase II inhibitor from muscle than has been reported for the inhibitor from liver, kidney, and placenta.
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PMID:Partial purification and characterization of the components of the neutral ribonuclease II-inhibitor system of normal and distrophic mouse skeletal muscle. 626

A 7.1 kb HindIII-XhoI fragment of E. coli DNA which contains the structural gene for ribonuclease II (rnb) has been cloned in the recombinant plasmid pDK24. At least two constitutively expressed genes are encoded on the fragment as shown by maxicell analysis. On denaturing polyacrylamide gels RNase II appears as a single 72,000 dalton species. The approximate site of transcription initiation of the rnb gene has been mapped. Although derivatives of E. coli harboring pDK24 contained 10-fold more RNase II activity that wild type strains without the plasmid, the degradation rate of mRNA was similar in all strains tested. Strains deficient in both RNase II and polynucleotide phosphorylase appear inviable.
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PMID:Amplification of ribonuclease II (rnb) activity in Escherichia coli K-12. 633 77

A new ribonuclease, RNase BN, has been identified and partially purified from a strain of Escherichia coli lacking RNase II and RNase D by using the artificial tRNA precursor tRNA-C-[14C]U as substrate. This enzyme is present in E. coli B but absent from the tRNA processing mutant strain BN which is unable to process extraneous 3' residues on certain phage T4-specified tRNA precursors. The properties of RNase BN clearly distinguish this enzyme from other known E. coli exoribonucleases. It is optimally active at pH 6.5 with 0.2 mM divalent cation and 0.2 M monovalent cation. It is most active against tRNA substrates containing nucleotide substitutions within the -C-C-A sequence and relatively inactive against other types of RNAs. This substrate specificity in vitro is consistent with a processing function in vivo. However, in contrast to the other processing enzymes whose function has been confirmed by mutation, RNase BN is an exoribonuclease. The presence of multiple RNases in E. coli and a strategy for their identification and separation are discussed.
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PMID:Ribonuclease BN: identification and partial characterization of a new tRNA processing enzyme. 634 80


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