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)

In an attempt to elucidate the role of carbohydrates on protein structure and dynamics in glycoproteins, ribonuclease B (RNase B), containing a single glycosylation site at Asn34, has been investigated and compared with the enzyme in the unglycosylated form (RNase A). RNase B consists of five glycoforms: Man5GlcNAc2, Man6GlcNAc2, Man7GlcNAc2, Man8GlcNAc2 and Man9GlcNAc2 (Man5-9GlcNAc2). The individual glycoforms Man1GlcNAc2 (synthetic) and Man5GlcNAc2 of RNase B have been studied to ascertain any specific effects of the different oligosaccharides. NMR measurement of amide-proton/deuterium exchange rates shows that glycosylation of the enzyme leads to the protection of amide-proton resonances from solvent exchange for a large number of residues, both in the vicinity of the glycosylation site (e.g. residues 29-34 and 35) and remote from it (e.g. residues 57-61 and 75-76). In addition, residues 10-13, 32, 34 and 35, which are observed to be protected from exchange as a result of glycosylation in the individual glycoforms Man1Glc-NAc2-RNase and Man5GlcNAc2-RNase (when compared with RNase A) are less protected in RNase B. This additional protection in the glycoforms Man1GlcNAc2-RNase and Man5GlcNAc2-RNase may arise from steric hindrance between the oligosaccharide and protein reducing solvent accessibility. The rates of solvent exchange of amide protons for residues 10-13, 32, 34 and 35 are dependent on the oligosaccharide moiety. The average amide-proton/deuterium exchange rate in Man6-9Glc-NAc2-ribonucleases for residues 10-13 and 35 is approximately three times greater than Man5Glc-NAc2-ribonuclease, while for residues 32 and 34 it is approximately 7-11 times greater. CD analysis of RNase A and RNase B revealed the carbohydrate moiety to have a small stabilizing effect (approximately 5 kJ/mol) on the protein.
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PMID:Effects of glycosylation on protein structure and dynamics in ribonuclease B and some of its individual glycoforms. 824 69

Purkinje cell toxicity is one of the characteristic features of the Gordon phenomenon, a syndrome manifested by ataxia, muscular rigidity, paralysis, and tremor that may lead to death (Gordon, 1933). Two members of the RNase superfamily found in humans, EDN (eosinophil-derived neurotoxin) and ECP (eosinophil cationic protein), cause the Gordon phenomenon when injected intraventricularly into guinea pigs or rabbits. We have found that another member of the RNase superfamily, an antitumor protein called onconase, isolated from Rana pipiens oocytes and early embryos, will also cause the Gordon phenomenon when injected into the cerebrospinal fluid of guinea pigs at a dose similar to that of EDN (LD50, 3-4 micrograms). Neurologic abnormalities of onconase-treated animals were indistinguishable from those of EDN-treated animals, and histology showed dramatic Purkinje cell loss in the brains of onconase-treated animals. The neurotoxic activity of onconase correlates with ribonuclease activity. Onconase modified by iodoacetic acid to eliminate 70% and 98% of the ribonuclease activity of the native enzyme displays a similar decrease in ability to cause the Gordon phenomenon. In contrast, the homologous bovine pancreatic RNase A injected intraventricularly at a dose 5000 times greater than the LD50 dose of EDN or onconase is not toxic and does not cause the Gordon phenomenon. A comparison of the RNase activities of EDN, onconase, and bovine pancreatic RNase A using three pancreatic RNA substrates demonstrates that onconase is orders of magnitude less active enzymatically than EDN and RNase A. Thus, another member of the RNase superfamily in addition to EDN and ECP can cause the Gordon phenomenon.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Toxicity of an antitumor ribonuclease to Purkinje neurons. 830 53

A chimeric cDNA was constructed, coding for the N-terminal region of BS-RNase (residues 1-49) and the C-terminal region of RNase A (residues 50-124). The resulting chimeric DNA was expressed in Escherichia coli and found to code for RNase chains that spontaneously assembled into a covalently dimeric ribonuclease.
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PMID:The determinants of the dimeric structure of seminal ribonuclease are located in its N-terminal region. 835 2

Cross-contamination with previously amplified products poses a serious limitation in the use of PCR for clinical testing and in certain research applications as well. In the present study we report the use of novel primers containing a 3'-terminal ribose residue to circumvent this problem. Extension of the primer by Taq DNA polymerase generates a cleavable ribonucleotide linkage within the amplified product. Cleavage of the primer by base or with a ribonuclease interferes with further replication of the product should carry over to another sample occur. Primers terminating in any of the 4 ribose residues function equally well as all DNA primers. Taq DNA polymerase is thus able to both efficiently extend and copy the single ribose residue. In translating from all DNA primers to ones containing a 3'-ribose residue no modification of the PCR protocol is required. The products formed can be used in all applications of the PCR. Since neither the original sample DNA, the primers or the extension products are modified by base or ribonuclease treatment both pre- and post-amplification sterilization can be carried out. Pre-amplification treatment with RNase A can yield as high as 10(4)-fold sterilization. Under these conditions the addition of beta-mercaptoethanol or other sulfhydryl reducing agent is necessary to inactivate the enzyme during thermocycling. Post-amplification treatment with NaOH readily yields at least 10(6)-fold sterilization. This alone is sufficient for most, if not all, applications of PCR. It is especially useful for quantitative RT-PCR, since the original target RNA sequence, which may be present in high copy numbers, is also destroyed.
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PMID:Use of PCR primers containing a 3'-terminal ribose residue to prevent cross-contamination of amplified sequences. 841 89

Interleukin 2 (IL2) mRNA has a short half-life in the cytoplasm of T lymphocytes, relative to most mRNA. We have discovered a candidate ribonuclease to account for the rapid turnover of IL2 mRNA in the cytosol of the human T lymphocyte cell line Jurkat. In partially purified form, this RNase is about 7 times as active on IL2 as on beta-globin mRNA. Pancreatic RNase, by contrast, does not show a significant preference for IL2 mRNA. Neither 5' capping, nor polyadenylation of the substrate mRNAs affects their degradation by the IL2-selective mRNase, whose activity is optimal in 0.5 mM Mg++ and 100 mM potassium acetate. The mRNase behaves like a protein of molecular weight 60-70,000 on gel chromatography, and is unusual in that it is insensitive to placental RNase inhibitor (RNasin). The mRNase cleaves IL2 mRNA at a small number of sites in the coding region, and IL2 mRNA containing only the coding region and 36 nucleotides of the 3'-noncoding region competes efficiently with full-length IL2 mRNA for the mRNase, whereas beta-globin mRNA does not.
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PMID:An RNasin-resistant ribonuclease selective for interleukin 2 mRNA. 844 10

Sialic acid-binding lectin (SBL) isolated from Rana catesbeiana eggs is a basic protein which agglutinates a large variety of tumour cells and has an amino acid sequence homologous to that of human angiogenin and pancreatic ribonuclease (RNase). Although SBL and angiogenin lack the Cys-65-Cys-72 disulphide bond of pancreatic RNase, the locations of the other three disulphide bonds are similar among the three molecules. SBL was found to exhibit RNase activity, as well as catalytic properties resembling those of bovine RNase A in some respects. For example, SBL hydrolyses poly(uridylic acid) and poly(cytidylic acid) as substrates, and prefers the former. RNase A and angiogenin are strongly inhibited by human placental RNase inhibitor, whereas the RNase activity and tumour cell agglutination activity of SBL are not affected by this inhibitor.
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PMID:Ribonuclease activity of sialic acid-binding lectin from Rana catesbeiana eggs. 844 85

Onconase, or P-30, is a protein initially purified from extracts of Rana pipiens oocytes and early embryos based upon its anticancer activity both in vitro and in vivo. It is a basic single-chain protein with an apparent molecular mass of 12,000 daltons and is homologous to RNase A. In cultured 9L glioma cells, onconase inhibits protein synthesis with an IC50 of about 10(-7) M. The inhibition of protein synthesis correlates with cell death determined by clonogenic assays. 125I-Labeled onconase binds to specific sites on cultured 9L glioma cells. Scatchard analysis of the binding data shows that onconase appears to bind to cells with two different affinities, one with a Kd of 6.2 x 10(-8) and another of 2.5 x 10(-7) M. Each cell could bind about 3 x 10(5) molecules of onconase at each of the two affinity sites. The low affinity Kd is similar to the IC50 for onconase toxicity. Onconase also demonstrates a saturability of cytotoxicity at a concentration that would saturate the low affinity binding site. Incubation at 4 degrees C increased the binding of onconase to cells relative to 37 degrees C binding and also increased the sensitivity of cells to onconase toxicity, indicating that receptor binding may be an initial step in cell toxicity. Onconase cytotoxicity can be blocked by metabolic inhibitors, NaN3 and 2-deoxyglucose, and cytotoxicity is potentiated 10-fold by monensin. Ribonuclease activity appears necessary for onconase toxicity because alkylated onconase, which only retains 2% of the ribonuclease activity, was at least 100-fold less potent in inhibiting protein synthesis in cells. Onconase inhibition of protein synthesis in 9L cells coincides with the degradation of cellular 28 S and 18 S rRNA. In contrast to RNase A, onconase is resistant to two RNase inhibitors, placental ribonuclease inhibitor and Inhibit-Ace. Northern hybridization with placental ribonuclease inhibitor cDNA probe indicates that 9L glioma cells contain endogenous placental ribonuclease inhibitor mRNA. Based on these results, we propose that onconase toxicity results from onconase binding to cell surface receptors, internalization to the cell cytosol where it degrades ribosomal RNA, inhibiting protein synthesis and causing cell death.
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PMID:A cytotoxic ribonuclease. Study of the mechanism of onconase cytotoxicity. 848 18

Bovine seminal ribonuclease (BS-RNase), a dimeric homolog of bovine pancreatic ribonuclease A (RNase A), is toxic to mammalian cells. In contrast to dimeric BS-RNase, a monomeric BS-RNase and RNase A are not cytotoxic and are bound tightly by cytosolic ribonuclease inhibitor. To elucidate the mechanism of ribonuclease cytotoxicity, we constructed a series of hybrid and semisynthetic enzymes and examined their properties. In five hybrid enzymes, divergent residues in BS-RNase were replaced with the analogous residues of RNase A so as to diminish an interaction with a putative cellular receptor. In a semisynthetic enzyme, the disulfide bonds that cross-link the monomeric subunits of dimeric BS-RNase were replaced with thioether bonds, which can withstand the reducing environment of the cytosol. Each hybrid and semisynthetic enzyme had ribonucleolytic and cytotoxic activities comparable with those of wild-type BS-RNase. These results suggest that dimeric BS-RNase (pI = 10.3) enters cells by adsorptive rather than receptor-mediated endocytosis and then evades cytosolic ribonuclease inhibitor so as to degrade cellular RNA. This mechanism accounts for the need for a cytosolic ribonuclease inhibitor and for the cytotoxicity of other homologs of RNase A.
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PMID:Mechanism of ribonuclease cytotoxicity. 853 70

The three-dimensional structure of ribonuclease Rh (RNase Rh), a new class of microbial ribonuclease from Rhizopus niveus, has been determined at 2.0 A resolution. The overall structure of RNase Rh is completely different from those of other previously studied RNases, such as RNase A from bovine pancreas and RNase T1 from Aspergillus oryzae. In the structure of RNase Rh, two histidine residues (His46 and His109) and one glutamic acid residue (Glu105), which were predicted to be critical to the activity from the chemical modification and mutagenesis experiments, are found to be located close together, constructing the active site. The indole ring of Trp49 plays an important role in preserving the active site structure by its stacking interactions with the imidazole ring of His 109, and by hydrogen bonding with the carboxyl group of Glu105. There exists a hydrophobic pocket around the active site, which contains the aromatic side-chain of Trp49 and Tyr57. The results of mutagenesis studies suggest that this pocket is the base binding site of the substrate.
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PMID:The crystal structure of ribonuclease Rh from Rhizopus niveus at 2.0 A resolution. 855 22

A rapid and efficient method for the preparation of highly pure meningococcal lipo-oligosaccharide (LOS) was developed. This used a Superose 6 column on a FPLC system to purify LOS from phenol-water extracts of cell lysates of Neisseria meningitidis. The purest LOS preparations, with no detectable protein contamination and less than 0.5% (w/w) residual RNA, were obtained when cell lysates had been treated with RNase ONE before phenol extraction and chromatographic separation. Preparations that had received no ribonuclease treatment had 2-3% residual RNA contamination and predigestion of samples with RNase A, which only partially degraded the RNA present in the crude extracts, resulted in LOS samples contaminated with 15-20% residual RNA. The LOS purified from RNase ONE-treated extracts was highly endotoxic, and showed no reduction in antibody binding or specific endotoxin activity compared to unpurified material. Approximately 80% of the LOS applied to the chromatography column was recovered as purified material.
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PMID:Purification of meningococcal lipo-oligosaccharide by FPLC techniques. 858 Nov 70


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