Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.1.27.4 (ribonuclease)
 6,621 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The presence of four members of the pyrimidine-specific ribonuclease superfamily was demonstrated in rat liver. Three of them (RL1, RL2 and RL3) were purified and showed ribonuclease activity at pH 7.5 with yeast RNA as substrate. RL1 is identical to rat pancreatic ribonuclease (ribonuclease 1). N-terminal sequence analysis showed the presence of the native protein and several N-terminally degraded components. RL2 and RL3 were N-terminally blocked proteins. After acidic cleavage or CNBr digestion, several parts of their sequences were determined. RL2 has high sequence similarity with neurotoxin-type ribonucleases (ribonucleases 2, 3 and 6). The amino acid sequence of rat liver-type ribonuclease (ribonuclease 4) was determined from a liver cDNA library. It differs at about 20% of the amino acid positions from other mammalian liver-type ribonucleases. The sequence of a peptide of RL3 was identical to that derived from the cDNA sequence of the liver-type ribonuclease. A contaminant of the RL3 fraction had a high sequence similarity with mouse and other mammalian angiogenins. Bovine, porcine and rat liver-type ribonucleases showed a strong preference for poly(U) over poly(C). This preference is a unique property of the liver-type enzymes of the ribonuclease superfamily.
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PMID:Ribonucleases from rat and bovine liver: purification, specificity and structural characterization. 960 56

Hammerhead ribozymes were used as substrates to examine endoribonucleolytic activities in cell extracts and cultured human cells. Primer-extension analyses showed that ribozymes directed against tumor necrosis factor-alpha mRNA and human immunodeficiency virus type 1 tat mRNA were cleaved at UA and CA dinucleotides by extracts. Preferred cleavage sites were similar to those observed following digestion with RNase A, and cleavage was blocked by RNasin, an inhibitor of pyrimidine-specific ribonucleases. Removal of UA and CA dinucleotides rendered ribozymes more stable when incubated in cell extracts that were not significantly contaminated by extracellular nucleases. Placement of UA dinucleotides adjacent to a ribozyme in mRNA led to excision of the ribozyme from long transcripts during incubation in extracts. UA dinucleotides also made mRNA more labile than a control RNA when expressed from an endogenous plasmid gene in the human myeloid cell line U937. Similarly, UA and CA dinucleotides caused ribozymes to have a shorter half-life when delivered to U937 cells by lipofectin-mediated transformation. Taken together, these data indicate that one or more members of the pyrimidine-specific ribonuclease family is involved in the intracellular degradation of RNA, and they explain the paucity of UA dinucleotides in eukaryotic mRNA. Judicious manipulation of preferred target sequences of pyrimidine-specific ribonucleases may be useful in designing effective hammerhead ribozymes.
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PMID:Degradation of hammerhead ribozymes by human ribonucleases. 964 39

Human extracellular ribonucleases (RNase), together with other members of the mammalian RNase A superfamily, can be classified into four different RNase families on the basis of their structural, catalytic and/or biological properties. Their occurrence and main distinctive features have been described, and the information available on their catalytic properties has been analysed and discussed in comparison with those of other animal RNases. On the basis of some results obtained with various single- and double-stranded polyribonucleotides, it has been proposed that while pancreatic-type (pt) RNases could be defined as single-strand/pyrimidine 'preferring' ribonucleases, mammalian nonpancreatic-type (npt) RNases may be referred to as single-strand/pyrimidine 'specific' ribonucleases. In addition, some data concerning human nptRNases may support the suggestion [Cuchillo et al. (1993) FEBS Lett. 333: 207-210] that the enzyme 'ribonuclease' should be reclassified as 'transferase'.
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PMID:Human extracellular ribonucleases: multiplicity, molecular diversity and catalytic properties of the major RNase types. 976 Sep 87

RC-RNase is a pyrimidine-guanine sequence-specific ribonuclease and a lectin possessing potent cell cytotoxicity. It was isolated from the oocytes of Rana catesbeiana (bull frog). From analysis of an extensive set of 1H homonuclear 2D NMR spectra we have completed the resonance assignments. Determination of the three-dimensional structure was carried out with the program X-PLOR using a total of 951 restraints including 814 NMR-derived distances, 61 torsion angles, and 76 hydrogen bond restraints. In the resultant family of 15 best structures, selected from a total of 150 calculated structures, the root-mean-square deviation from the average structure for the backbone heavy-atoms involved in well-defined secondary structure is 0.48 A, while that for all backbone heavy-atoms is 0.91 A. The structure of RC-RNase consists of three alpha-helices and two triple-stranded anti-parallel beta-sheets and folds in a kidney-shape, very similar to the X-ray crystal structure of a homolo gous protein, onconase isolated from Rana pipiens. We have also investigated the interaction between RC-RNase and two inhibitors, cytidylyl(2'-->5')guanosine (2',5'-CpG) and 2'-deoxycytidylyl(3'-->5')-2'-deoxyguanosine (3',5'-dCpdG). Based on the ligand-induced chemical shift changes in RC-RNase and the NOE cross-peaks between RC-RNase and the inhibitors, the key residues involved in protein-inhibitor interaction have been identified. The inhibitors were found to bind in a "retro-binding" mode, with the guanine base bonded to the B1 subsite. The His103 residue was found to occupy the B state with the imidazole ring pointing away from the active site. The structure coordinates and the NMR restraints have been deposited in the Brookhaven Protein Data Bank (1bc4 and 1bc4mr, respectively).
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PMID:The solution structure of a cytotoxic ribonuclease from the oocytes of Rana catesbeiana (bullfrog). 976 86

Bovine seminal ribonuclease (BS-RNase) is a unique member of the pancreatic-like ribonuclease superfamily. The native enzyme is a mixture of two dimeric forms with distinct structural features. The most abundant form is characterized by the swapping of N-terminal fragments. In this paper, the crystal structure of the complex between the swapping dimer and uridylyl(2',5')adenosine is reported at 2.06 A resolution. The refined model has a crystallographic R-factor of 0.184 and good stereochemistry. The quality of the electron density maps enables the structure of both the inhibitor and active site residues to be unambiguously determined. The overall architecture of the active site is similar to that of RNase A. The dinucleotide adopts an extended conformation with the pyrimidine and purine base interacting with Thr45 and Asn71, respectively. Several residues (Gln11, His12, Lys41, His119, and Phe120) bind the oxygens of the phosphate group. The structural similarity of the active sites of BS-RNase and RNase A includes some specific water molecules believed to be relevant to catalytic activity. Upon binding of the dinucleotide, small but significant modifications of the tertiary and quaternary structure of the protein are observed. The ensuing correlation of these modifications with the catalytic activity of the enzyme is discussed.
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PMID:Binding of a substrate analog to a domain swapping protein: X-ray structure of the complex of bovine seminal ribonuclease with uridylyl(2',5')adenosine. 1008 66

Bovine pancreatic ribonuclease A (RNase A) is a distributive endoribonuclease that catalyzes the cleavage of the P-O5' bond of RNA on the 3' side of pyrimidine residues. Here, RNase A is shown to cleave the P-O5' bond of a pyrimidine ribonucleotide faster when the substrate is embedded within a longer tract of poly(adenylic acid) [poly(A)] or poly(deoxyadenylic acid) [poly(dA)]. These data indicate that a ribonuclease can diffuse in one dimension along a single-stranded nucleic acid. This facilitated diffusion is mediated by Coulombic interactions, as the extent is diminished by the addition of NaCl. RNase A is more effective at cleaving a pyrimidine ribonucleotide embedded within a poly(dA) tract than within a poly(deoxycytidylic acid) [poly(dC)] tract. T45G RNase A, which catalyzes the processive cleavage of poly(A) but the distributive cleavage of poly(cytidylic acid) [poly(C)], has the same preference. Apparently, processive catalysis by the T45G enzyme arises from the expanded substrate specificity of the variant superimposed upon an intrinsic ability to diffuse along poly(A). Homologous ribonucleases with cytotoxic activity may rely on facilitated diffusion along poly(A) tails for efficient degradation of the essential information encoded by cellular mRNA.
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PMID:Extending the limits to enzymatic catalysis: diffusion of ribonuclease A in one dimension. 1022 Mar 16

RC-RNase purified from Rana catesbeiana (bullfrog) oocytes is a pyrimidine-guanine sequence-specific ribonuclease. RC-RNase is derived from the RNase superfamily genes exerting distinct ribonucleolytic activity and possesses cytotoxicity to tumor cells, but rarely to primary cells. In this study, we utilized RC-RNase to function with antiproliferative cytokines. The combination with TNF-alpha or TNF-beta would not aggravate cell death. However, the combination with IFN-gamma could induce synergistic cytotoxicity verified by XTT assays toward three hepatoma cell lines bearing different differentiation stages. The distinct cytotoxicity from RC-RNase or RC-RNase/IFN-gamma on different hepatoma cells was correlated with the differentiation extent but not the proliferation rate of the cells. Despite the synergistic cytotoxicity and severe mitochondrial disruptions in the RC-RNase/IFN-gamma-treated cells, we scarcely detected any significant feature of apoptosis or necrosis by FACS analysis on annexin-V/propidium iodide staining. The mechanisms of cell death triggered by RC-RNase or RC-RNase/IFN-gamma require further investigation.
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PMID:Synergistic cytotoxicity of Rana catesbeiana ribonuclease and IFN-gamma on hepatoma cells. 1116 59

Five to 20% linear sucrose gradients were used to obtain sedimentation patterns of mycobacterial ribosomes, ribosomal subfractions, and ribonucleic acid (RNA) preparations. Classical 70S ribosomes were obtained when 10(-1)m magnesium chloride was used. These, when dialyzed against 10(-4)m MgCl(2), yielded typical 50S, 30S, and smaller ribosomal subunits. The 30S subunits were the most immunogenic under these conditions. A ribosomal preparation containing subunits which varied from 2.5 to 40S was fractionated by collecting five fractions from a sucrose gradient; based upon the amount of nucleic acid present, the fraction containing the 40S particles was most immunogenic. Physical and chemical evidence suggested that mycobacterial RNA preparations extracted with 65% ethyl alcohol from the ribosomes and diluted in distilled water, were either double-stranded, or mostly double-helical, or had a highly organized secondary structure. This was based on the following observations. (i) Native RNA was resistant to trace amounts of ribonuclease. (ii) The approximate T(m) value in SSC buffer (0.15 m NaCl plus 0.015 m sodium citrate) was greater than 85 C and in 0.1 SSC buffer was 55 C; the RNA diluted in SSC buffer produced a hypochromic effect on cooling at room temperature. (iii) Formaldehyde, in the presence of SSC buffer, decreased the T(m) of the RNA to approximately 55 C, and there was no hypochromic effect on cooling. (iv) Formaldehyde did not increase the wavelength of maximal adsorption of the RNA. (v) The purine/pyrimidine ratio was close to one. (vi) The major peak of the RNA sedimented in the more dense zones of the sucrose gradients. There was a relationship between the sedimentation pattern obtained with the RNA-protein subunits on sucrose gradients and immunogenicity; several examples are given. RNA-protein complexes of approximately 14 to 20S, and occasionally 23S in the major peak, appeared to produce the highest immune response. Smaller RNA-protein complexes such as 6S, which were obtained when the RNA preparation was diluted in certain buffers, were much less immunogenic. This was confirmed by collecting five fractions from sucrose gradients and finding the third fraction (containing RNA-protein complexes approximately 15 to 16S) the most immunogenic. Immunogenic activity was apparently related to the structure of the RNA since it was maximal when the RNA appeared to be either double stranded, double helical, or had a highly organized structure.
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PMID:Immunogenic mycobacterial ribosomal and ribonucleic Acid preparations: chemical and physical characteristics. 1655 92

The rapid degradation of ribonucleic acids (RNA) by ubiquitous ribonucleases limits the efficacy of new therapies based on RNA molecules. Therefore, our aim was to characterize the natural ribonuclease activities on the skin and in blood plasma i.e. at sites where many drugs in development are applied. On the skin surfaces of Homo sapiens and Mus musculus we observed dominant pyrimidine-specific ribonuclease activity. This activity is not prevented by a cap structure at the 5'-end of messenger RNA (mRNA) and is not primarily of a 5'- or 3'-exonuclease type. Moreover, the ribonuclease activity on the skin or in blood plasma is not inhibited by chemical modifications introduced at the 2'OH group of cytidine or uridine residues. It is, however, inhibited by the ribonuclease inhibitor RNasin although not by the ribonuclease inhibitor SUPERase* In. The application of our findings in the field of medical science may result in an improved efficiency of RNA-based therapies that are currently in development.
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PMID:Characterization of the ribonuclease activity on the skin surface. 1673 88

1. ADP, ATP and GDP inhibited the phosphotransferase activity, the release of cyclic nucleotides from RNA, of ribonuclease. No significant inhibition was elicited by pyrimidine 5'-nucleoside diphosphates, CDP and UDP. 2. Inhibition by ADP, AMP, adenosine, adenine, NAD and NADP was insignificant at the concentrations tested. Small inhibition was observed with high concentrations of AMP and only when soluble RNA was the substrate. 3. Inhibition by ADP was found to be ;uncompetitive'. 4. Results seem to indicate that at least for optimum inhibition the polyphosphate of the purine nucleoside is essential. They further suggest that the inhibitor acts by combining with the enzyme only when the enzyme is bound to the substrate.
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PMID:Effect of nucleoside 5'-di- and 5'-tri-phosphates on pancreatic ribonuclease activity. 1674 35


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