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)

Cytoplasmic 10S ribonucleoprotein (iRNP) is a potent inhibitor of mRNA translation in vitro and contains a 4 S translation inhibitory RNA species (iRNA) (Sarkar, S., Mukherjee, A. K., and Guha, C. (1981) J. Biol. Chem. 256, 5077-5086). This ribonucleoprotein has now been resolved into protein and RNA components by DEAE-cellulose chromatography in the absence of both K+ and Mg2+ ions. These cations are required for maintaining the nucleoprotein structure of iRNP. Incubation of the dissociated protein and RNA components in the presence of K+ and Mg2+ at 35 degrees C reconstitutes a 10 S particle which is indistinguishable from native iRNP with respect to the elution profile by gel filtration, UV spectra, buoyant density, resistance to pancreatic RNase, and ability to inhibit exogenous mRNA translation in vitro. Chick muscle tRNA and globin mRNA could not form an RNP complex with the protein moieties of iRNP. The separated proteins, unlike iRNA and iRNP, do not inhibit mRNA translation. Their function may be to protect iRNA from ribonuclease digestion, since iRNP is ribonuclease-resistant. The ability to dissociate the iRNP particle and to specifically reconstitute it from the separated components indicates that it is a unique cellular entity which is distinct from other ribonucleoproteins.
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PMID:The translational inhibitor 10 S cytoplasmic ribonucleoprotein of chick embryonic muscle. Dissociation and reassociation. 728 68

Acid ribonuclease (ribonucleate-3'-oligonucleotide hydrolase, EC 3.1.4.23) has been isolated from the lysosomal fraction of Bombyx mori eggs. The enzyme has a pH optimum of 4,7 and a molecular weight of 17 000 +/- 1000; the isoelectric point of the enzyme lies around 6,0. The enzyme splits RNA and poly(U) down to nucleoside-3'-phosphates to form intermediates--nucleoside-2',3'-cyclophosphates. Polyadenylic acid is hydrolyzed in the presence of the enzyme down to oligonucleotides. Mg2+ suppress the enzyme activity.
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PMID:[Isolation, purification and properties of acid ribonuclease from the lysosomal fraction of silkworm eggs]. 737 3

Protein B23 is an abundant nucleolar protein and putative ribosome assembly factor. The protein was analyzed for ribonuclease activity using RNA-embedded gels and perchloric acid precipitation assays. Three purified bacterially expressed forms of the protein, B23.1, B23.2 and an N-terminal polyhistidine tagged B23.1 as well as the natural protein were found to have ribonuclease activity. However, the specific activity of recombinant B23.1 was approximately 5-fold greater than that of recombinant B23.2. The activity was insensitive to human placental ribonuclease inhibitor, but was inhibited by calf thymus DNA in a dose dependent manner. The enzyme exhibited activity over a broad range of pH with an apparent optimum at pH 7.5. The activity was stimulated by but not dependent on the presence of low concentrations of Ca2+, Mg2+ or NaCl. The Ca2+ effect was saturable and only stimulatory in nature. In contrast, Mg2+ and NaCl exhibited optimal concentrations for stimulation and both inhibited the ribonuclease at concentrations above these optima. These data suggest that protein B23 has intrinsic ribonuclease activity. The location of protein B23 in subcompartments of the nucleolus that contain preribosomal RNA suggests that its ribonuclease activity plays a role in the processing of preribosomal RNA.
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PMID:The ribonuclease activity of nucleolar protein B23. 747 45

To study the interaction and the role of the metal ion in the reaction catalyzed by Escherichia coli ribonuclease HI (E. coli RNase HI), substrate analogues containing a phosphorothioate linkage or 2'-modified nucleosides at the cleavage site were used. In the presence of Mg2+, Mn2+, Co2+, Zn2+, or Cd2+, the phosphorothioate linkage with the RP-configuration was cleaved, while the SP-isomer was not. Kinetic studies showed that Mn2+ and Cd2+ facilitated the cleavage of the phosphorothioate to only a small extent, which indicated the absence of an interaction between the metal ion and this phosphate residue. The interaction of the metal ion with the 2'-functional group was analyzed by Mg(2+)-titration experiments using the -OH, -NH2, and -F substrates. From Hill plots, it was found that the KMg values were almost the same. These results are evidence of an interaction between Mg2+ and the 2'-functional group by the formation of an outer-sphere complex with a water molecule. The Hill coefficient of 1.0 for the -OH substrate indicated that a single Mg2+ ion is required for the catalysis.
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PMID:Role of the Mg2+ ion in the Escherichia coli ribonuclease HI reaction. 770 24

All of the individual carboxyl groups (the side-chain carboxyl groups of Asp and Glu, and the C-terminal alpha-carboxyl group) in Escherichia coli ribonuclease HI, which is an enzyme that cleaves the RNA strand of a RNA/DNA hybrid, were pH-titrated, and their ionization constants (pKa) were determined from an analysis of the pH-dependent chemical shifts of the carboxyl carbon resonances obtained from 1H-13C heteronuclear two-dimensional NMR. The pKa values in the enzyme varied widely among individual residues, for example, in the unusual pKa values for two important catalytic residues, Asp10 (pKa 6.1) and Asp70 (pKa 2.6). Moreover, remarkable two-step titrations were observed for these carboxylates. The binding of Mg2+ ion to the enzyme, which is the cofactor necessary for catalytic activity, caused no significant change in the pKa values of the carboxyl groups, except for that of Asp10. The variations of the pKas that were dependent on the microenvironment in the protein were theoretically reproduced to compare with the experimental results by a numerical calculation, using a continuum electrostatic model. Most of the significant pKa decreases were brought about through strong electrostatic interactions with the neighboring basic amino acids, Arg or Lys. The pKa shifts and the two-step titrations of Asp10 and -70, which are close to each other, were interpreted to be due to the neighboring effect of two functional groups, as observed in the interacting titratable groups of a dicarboxyl compound or in the active site carboxylates of lysozyme and aspartic protease. The role of Asp10 in the catalytic action is either to be the proton donor to the RNA moiety or the binding partner of the Mg2+ ion cofactor. Asp70, on the other hand, is considered to be the proton acceptor from a water molecule.
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PMID:Individual ionization constants of all the carboxyl groups in ribonuclease HI from Escherichia coli determined by NMR. 790 91

Although ribonucleases fold into correct tertiary conformation in vitro guided solely by information contained in the primary amino acid sequence (Sela, M., White, F. H., and Anfinsen, C. B. (1957) Science 124, 691-693), it is not clear whether folding of these proteins proceeds unassisted in a complex intracellular environment. We describe here the specific and high affinity binding of groEL, the prokaryotic homolog of the heat shock protein 60 family of molecular chaperones, to recombinant eosinophil cationic protein and eosinophil-derived neurotoxin, two members of the human ribonuclease gene family. We have determined that groEL binds to a unique peptide sequence near the amino terminus of nascent eosinophil cationic protein that includes the first of eight cysteine residues. This binding site functions independently and can confer groEL binding activity on an unrelated carrier protein. GroEL dissociates from the binding site upon addition of ATP and Mg2+; no other cations or cofactors are necessary. These findings suggest the possibility that interaction with a groEL-like molecular chaperone may be a requirement for correct folding and/or translocation of eukaryotic ribonucleases in vivo.
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PMID:Characterization of a distinct binding site for the prokaryotic chaperone, GroEL, on a human granulocyte ribonuclease. 809 49

The small prohead RNA (pRNA) of the Bacillus subtilis bacteriophage phi 29 is essential for ATP-dependent packaging of viral DNA. The 174-, 124-, and 120-residue forms of pRNA produced in vitro using T7 RNA polymerase were equivalent in prohead binding and DNA packaging activity to pRNAs produced in phi 29-infected cells. pRNA binding to proheads, characterized by the use of Northern hybridization and filter binding assays, was specific, rapid, and irreversible in the presence of 10 mM Mg2+. Proheads produced in phage-infected cells carried 5.8 +/- 2.7 copies of pRNA, and proheads assembled in Escherichia coli in the absence of pRNA bound 6.0 +/- 3.5 copies of pRNA. Footprints of proheads on pRNA generated with the ribonucleases A, T1, and V1 showed that nucleotides 22-84, 5' to 3', were protected from ribonuclease attack. Enhanced cleavage at nucleotides 37-40 with ribonuclease V1 suggested a conformational change of pRNA upon prohead binding.
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PMID:Characterization of the prohead-pRNA interaction of bacteriophage phi 29. 810 96

Structural differences between native (modified) and in vitro transcribed (unmodified) Escherichia coli tRNA(Val) were explored by comparing their temperature-absorbance profiles as a function of magnesium ion concentration and by probing their solution conformation with single- and double-strand-specific endonucleases. In vitro transcribed tRNA(Val) has a less ordered structure as monitored by thermal melting profiles; its Tm is appreciably lower than that of native tRNA(Val) at all Mg2+ concentrations. Structure probing experiments with nuclease S1 and ribonuclease V1 show that the unmodified tRNA(Val) transcript is more susceptible to nuclease attack at low Mg2+ concentrations, particularly in the D- and T-loops, indicative of at least a partial disruption of D-loop/T-loop interactions. These experiments also provide evidence for temperature-dependent alternative conformations of the anticodon loop of native tRNA(Val). Modified nucleosides are essential for the stability of these conformers; they cannot be detected in the unmodified in vitro transcript. The observations suggest that post-transcriptional modifications in tRNA allow the adoption of unique conformations and act to stabilize those that are biologically active.
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PMID:Probing structural differences between native and in vitro transcribed Escherichia coli valine transfer RNA: evidence for stable base modification-dependent conformers. 817 44

We have purified a Ca2+ dependent ribonuclease from the oocytes of Xenopus leavis. Two properties of this ribonuclease set it apart from other known nucleases. First, Ca2+ was required for ribonuclease activity, and Mg2+ would not substitute. Second, the enzyme specifically degraded RNA and digestion of double or single stranded DNA was not observed. Ca2+ dependent ribonuclease activity of the purified 36-kDa protein was directly observed after renaturation of the protein following electrophoresis in an SDS-Laemmli gel. In addition, the enzyme was shown to have endoribonuclease activity at numerous sites. The Ca2+ dependence suggests that the ribonuclease activity may be modulated by changes in the level of intracellular Ca2+ and thereby provide a direct link to signal transduction systems.
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PMID:Purification of a calcium dependent ribonuclease from Xenopus laevis. 819 Jun 37

A nucleolar endoribonuclease from mouse Ehrlich ascites tumor cells, that has been implicated in the endonucleolytic cleavage of mouse precursor ribosomal RNA, specifically and stably binds an in vitro-derived rRNA transcript containing the +650 early processing site. The specificity of binding was demonstrated by mobility shift analysis, glycerol gradient velocity sedimentation analysis, and UV-crosslinking studies. Binding did not require Mg2+ and therefore was not dependent on cleavage; however, binding was dependent on the presence of the early +650 processing site since a pre-rRNA transcript with the +650 processing site deleted failed to compete in binding. A small nucleolar RNA component was not required for the formation of this stable complex or for the specific cleavage of a processing competent pre-rRNA transcript. UV crosslinking studies using 32P-labeled 5-azidouridine-substituted pre-rRNA with bound nucleolar endoribonuclease identified three closely sized polypeptides of approximately 50, approximately 48, and approximately 45 kDa, respectively, that specifically crosslinked to the processing competent rRNA transcript. These three polypeptides species were identified following ribonuclease digestion and electrophoresis on a SDS-polyacrylamide gel. An identical pattern of labeled polypeptides was also identified from gel mobility shift analysis where the specifically shifted material was U.V. crosslinked. The largest of these polypeptides corresponded to the estimated size of the nucleolar endoribonuclease, while the lower molecular weight species may represent partially proteolyzed enzyme. Overall, these results suggest that the unique specificity of the nucleolar endoribonuclease may, in part, be attributed to the formation of a stable complex at the +650 processing site for mouse preribosomal RNA, and that formation of this unique stable complex affords a means to specifically label the limited amount of available partially purified enzyme for sequence analysis.
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PMID:Selection of a preribosomal RNA processing site by a nucleolar endoribonuclease involves formation of a stable complex. 828 28


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