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:3.1.27.5 (RNase)
17,967 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Simian virus 40 large tumor antigen was isolated by immunoaffinity chromatography from monkey or mouse cell cultures undergoing lytic or transforming infection. RNase-treated gel-purified large tumor antigen, on hydrolysis with alkali, gave about equimolar amounts of AMP, GMP, CMP, and UMP. Furthermore, RNA fragments of approximately 45 nucleotides could be isolated from large tumor antigen purified by the same procedure. Mapping of the T1 oligonucleotides showed a high complexity, as indicated by the presence of unique sequences of 15-30 nucleotides and of poly(A). This is compatible with the hypothesis that these RNA fragments are derived from cellular pre-mRNAs or mRNAs. Our results suggest that Simian virus 40 large tumor antigen is a RNA-binding protein and might possibly be involved in regulation of synthesis, maturation, or translation of cellular mRNAs.
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PMID:Simian virus 40 large tumor antigen: a "RNA binding protein"? 617 63

Upon digestion with a streptococcal extracellular nuclease, yeast RNA yielded acid-insoluble core having increased carrier activity for streptolysin S. The carrier activity was found in minor fractions of the core which were eluted from a DEAE-cellulose column at higher salt concentrations. Upon gel filtration through a Sephadex G-75 column, the effective component (Fr. I) was eluted earlier than bulk oligonucleotides (Fr. II). Nucleotide composition (in mol %) of Fr. I was AMP: 21.8; GMP: 55.1; CMP: 8.2; UMP: 14.9, whereas that of Fr. II was AMP: 38.0; GMP: 33.1; CMP: 8.0; UMP: 20.9. Chromatographic patterns of SLS complex induced by Fr. I were similar to those of the toxin formed in the presence of active fraction prepared from RNase I core. Hemolytic activity of the latter complex was, like the former, unaffected by streptococcal nuclease treatment. The carrier activity of DNA digested with the nuclease was also investigated.
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PMID:Effect of streptococcal extracellular nuclease on the carrier activity of RNA for streptolysin S. 630 10

The helix content of rRNA species (Escherichia coli, Caldariella acidophila, rat liver) and the G . C content of their bihelical domains have been investigated by chemical modification of uracil and cytosine residues with probes specific for sterically exposed bases. By using radioactively labelled rRNA, G . C base pairs and the sum of A . U plus G . U base pairs have been quantified assuming that they are numerically identical with the unreactive cytosine and uracil rings, respectively. Exposed uracil bases were probed by their conversion to alkali-labile, nonultraviolet-absorbing sulphonated adducts, with 1.33 M bisulfite pH 7, at 20 degrees C; the adducts can be separated from unreacted uracil, and quantified, by cation-exchange chromatography of RNase T2 plus pancreatic RNase digests of bisulfite-modified rRNA. Exposed cytosines were probed by their conversion to methoxyaminated, alkali-stable, derivatives with 1 M methoxyamine, pH 5.5, at 37 degrees C, and quantified by monitoring the CMP/AMP radioactivity ratio after alkaline hydrolysis of modified rRNA. Exposed uracil rings can also be estimated spectrophotometrically by the alkali-catalyzed reversal of the non-ultraviolet-absorbing sulphonated adducts after separation of the latter from unreacted uracil. The cytosine deamination reaction, catalyzed by bisulfite at pH 6, has also been investigated and found to exhibit little specificity for sterically exposed bases of rRNA, the (G + C)-richer rRNA species of C. acidophila being considerably less susceptible to non-specific deamination than the (G + C)-poorer rRNA of E. coli. A high degree of congruence is shown to exist between results obtained by chemical modification and melting hyperchromicity experiments.
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PMID:Characterization of the secondary structure features of Escherichia coli, Caldariella acidophila and mammalian ribosomal RNA species by chemical modification of sterically exposed bases. 675 13

The refolding kinetics of guanidine-denatured disulfide-intact bovine pancreatic ribonuclease A (RNase A) and its proline-42-to-alanine mutant (Pro42Ala) have been studied by monitoring tyrosine burial and 2'-cytidine monophosphate (2'CMP) inhibitor binding. The folding rate for wild-type RNase A is faster in the presence of the inhibitor 2'CMP than in its absence, indicating that the transition-state structure in the rate-determining step is stabilized by 2'CMP. The folding rate monitored by 2'CMP binding to the major slow-folding species of Pro42Ala RNase A is faster than the folding rate monitored by tyrosine burial; however, the folding rate monitored by inhibitor binding to the minor slow-folding species is decreased significantly over the folding rate monitored by tyrosine burial, indicating that the major and minor slow-folding species of Pro42Ala fold to the native state with different transition-state conformations in the rate-determining step.
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PMID:Folding pathway of guanidine-denatured disulfide-intact wild-type and mutant bovine pancreatic ribonuclease A. 798 44

The crystal structure of human angiogenin (reported in the preceding paper in this issue) reveals that the site that corresponds to the pyrimidine binding site of RNase A is obstructed by Gln-117. Mutation of this residue to Ala and Gly is here found to increase activity 11- to 18-fold and 21- to 30-fold, respectively, toward dinucleotide, polynucleotide, and cyclic nucleotide substrates, but without changing specificity. The enhanced activity of Q117G toward CpA is due to a 5-fold decrease in Km and a 6-fold increase in kcat. Its Ki value for 2'-CMP is 5-fold lower than that of native angiogenin, whereas its Ki value for 5'-AMP is unchanged. It has been reported previously that mutating Asp-116 to Ala increases activity 15-fold. The double mutant D116A/Q117A is shown to be only slightly more active than each individual mutant. The present results demonstrate that Gln-117 impedes the ribonucleolytic activity of angiogenin, as predicted by x-ray crystallography. Moreover, they suggest that prior to or during catalysis angiogenin must undergo a conformational change to reorient the C-terminal segment that contains this residue, and that a similar reorganization is required for the mutants as well. This view is supported by molecular modeling of an angiogenin-uridine vanadate complex. These in vitro findings have implications for the angiogenic activity of angiogenin in vivo.
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PMID:Role of glutamine-117 in the ribonucleolytic activity of human angiogenin. 815 80

Different modes of binding of pyrimidine monophosphates 2'-UMP, 3'-UMP, 2'-CMP and 3'-CMP to ribonuclease (RNase) A are studied by energy minimization in torsion angle and subsequently in Cartesian coordinate space. The results are analysed in the light of primary binding sites. The hydrogen bonding pattern brings out roles for amino acids such as Asn44 and Ser123 apart from the well known active site residues viz., His12,Lys41,Thr45 and His119. Amino acid segments 43-45 and 119-121 seem to be guiding the ligand binding by forming a pocket. Many of the active site charged residues display considerable movement upon nucleotide binding.
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PMID:Computer modelling studies of ribonuclease A-pyrimidine nucleotide complexes. 828 64

As a first step toward the development of stable, selective, and potent inhibitors of those members of the pancreatic RNase superfamily that induce biological responses, we have focussed on low molecular weight compounds and studied their interactions with the active-site of bovine pancreatic ribonuclease A (RNase A). A new inhibitor is described, 5'-diphosphoadenosine 3'-phosphate, which binds to RNase A more tightly than any previous low molecular weight compound: its Ki value of 1.3 microM at pH 7 is 8-fold lower than that for uridine-vanadate, a transition-state analog, and 110-fold lower than that for 2'-CMP, one of the best-characterized RNase A ligands. The new inhibitor is found to contact RNase A residues that are conserved in several homologous mammalian RNases and hence should be able to serve as a basis for the design of even tighter-binding inhibitors of these enzymes.
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PMID:5'-Diphosphoadenosine 3'-phosphate is a potent inhibitor of bovine pancreatic ribonuclease A. 907 Aug 68

Labeling of 21-kDa material was observed when bovine brain soluble fraction was incubated with [adenylate-32P]NAD+ in the presence of GTP. The 21-kDa substrate, slightly smaller than C3 substrate in size, was labeled even without C3 exoenzyme. GTP could be replaced by nucleoside triphosphates other than ATP while ATP inhibited the GTP-induced labeling of 21-kDa substrate. After incubation of the soluble fraction with [adenylate-32P]NAD+ in the presence of GTP, [32P]ADP and [32P]ATP were detected in addition to [32P]AMP and [32P]ADP-ribose while only the last two nucleotides were observed without GTP. The 21-kDa substrate was labeled with [alpha-32P]ATP even in the absence of GTP, suggesting adenylylation rather than ADP-ribosylation. The labeled 21-kDa substrate, was extractable by phenol, disappeared with RNase treatment but not with tryptic digestion. Alkaline treatment of the phenol extract yielded an equal mixture of 3'-[32P]CMP and 2'-[32P]CMP. From these results we concluded that the 21-kDa labeling is a result of tRNA tailing with [alpha-32P]ATP generated from the [32P]AMP moiety of [adenylate-32P]NAD+. Results from reconstitution experiments using enzymes and tRNA purified from bovine brain soluble fraction, which are involved in this pathway, confirmed our conclusion.
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PMID:GTP-dependent modification of a 21-kDa substrate with NAD+ in bovine brain soluble fraction is not ADP-ribosylation of small G-protein but tailing of tRNA. 935 90

Four, widely used, ribonucleases were found to protect their substrates from acid precipitation by causing, evidently, a modification of their physicochemical properties. The protection was dependent on the kind of substrate while the ratio of protective to nucleolytic activity varied widely between the four enzymes. The protection was enhanced by some nucleotides like UMP, CMP and IMP and decreased in the presence of several bivalent ions like Zn++, Co++ and Cu++. It was completely abolished when the substrates were hybridized with their complementary ribohomopolymers. In the case of bovine pancreatic ribonuclease, the part of the molecule which was responsible for the protective activity was localized on the enzyme domain characterized as S-protein, which lacks nucleolytic activity. The observed property of ribonucleases could lead to false data when the measurement of TCA-soluble material is the method used to follow the purification of ribonucleases or to study their activity. It was also found that ribonuclease S-protein enhances the catalytic activity of B. Cereus RNAse. S-protein could potentiate other RNAses activity like onconase, which has recently been used as an anticancer agent.
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PMID:Ribonucleases protect RNA from acid precipitation. 948 43

The enthalpy of a reaction is most often determined through one of two means; it can be determined directly using calorimetry or indirectly by measuring the temperature dependence of the equilibrium constant (i.e., the van't Hoff method). Recently, discrepancies have been noted between the enthalpy measured by calorimetry, and the enthalpy determined by the van't Hoff method,. This has been suggested to indicate that the binding reaction is more complex than the simple one-to-one binding model used to describe the data. To better understand possible discrepancies between and, we have undertaken both experimental studies using isothermal titration calorimetry to measure the binding energetics of Ba(2+) binding 18-crown-6 ether and 2'-CMP binding RNase A, along with a simulation of a system involving a molecule in conformational equilibrium coupled with binding. We find that when experimental setup and analysis are correctly performed, no statistically significant discrepancies between and exist even for the linked system.
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PMID:Van't Hoff and calorimetric enthalpies from isothermal titration calorimetry: are there significant discrepancies? 1132 39


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