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)

At 2 degrees and 30 degrees C, enteroviruses are more stable on the acid than on the alkaline side of neutrality. In the range from pH 3 to 9, temperature is so influential that the fastest inactivation rate at 2 degrees C is slower than the slowest inactivation rate at 30 degrees C. Specific ions or salts also affect the rate of inactivation of enteroviruses. NaCl and other chloride salts enhance the inactivation of poliovirus at pH 3. NaCl is considerably less effective against poliovirus in the range of pH 4.5 to 7.0 than at pH less than 4.5. Loss of RNA infectivity of the virus particle proceeds as rapidly as the loss of infectivity of the particle itself, except at pH 3 in the presence of MgCl2. Inactivation results in alterations to the physical integrity of enteroviruses. At pH 5 and 7, RNA hydrolysis of poliovirus particles occurs; and at pH3, 5,6, and 7 the nucleic acid becomes susceptible to ribonuclease. Only virus particles inactivated at pH 3 show a sensitivity to chymotrypsin. The hemagglutinins of echovirus type 7 are destroyed during inactivation at pH 3,4,5, and 6; but at pH 6 this alteration precedes the loss of infectivity. The pH of the suspension is a primary determinant of the mechanism of virus destruction and possibly of the loss of infectivity at these temperatures.
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PMID:Effect of acid pH, salts, and temperature on the infectivity and physical integrity of enteroviruses. 1 66

Synthesis of cellular protein was substantially inhibited within 1 h of infection with herpes simplex virus, type 2, strain G (HSV-2). The inhibition also occurred, although no virus-specific protein synthesis was detected, after infection with u.v. irradiated virus and in cytoplasts that had been enucleated before infection. The inhibitory activity could not be distinguished from infectivity by dilution, sedimentation or reaction with gamma-globulin. HSV-2 also suppresssed the synthesis of Sendai virus proteins, but not those specified by HSV-1. Host protein synthesis was no more sensitive than virus protein synthesis to an increased concentration of NaCl in the medium, nor could the suppression of host synthesis be prevented by adding excess MgCl2 to the medium or by omitting CaCl2 or NaCl. It was accompanied by the breakdown of polyribosomes, which also occurred in the presence of cycloheximide but not at 4 degrees C. The breakdown yielded ribosomes that were sensitive to a high salt concentration, unlike those produced by treatment of polyribosomes with RNase. The synthesis of cellular DNA and RNA was also inhibited following infection with u.v.-inactivated virus. It is concluded that the suppression of host protein synthesis (and probably also of host DNA and RNA synthesis) is caused by a constituent of the infecting virus particles. The mechanism is obscure but probably does not depend on the leakage out of the cell of Mg2+ or into the cell or Ca2+ or Na+ ions, nor on the specific inhibition of initiation of host polypeptide chains, nor on RNase-like attack on host polyribosomes.
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PMID:Suppression of the synthesis of cellular macromolecules by herpes simplex virus. 21 20

Preparations of radioactive lysosomes were obtained from mouse kidney after injection of radioactive iodine-labeled bovine ribonuclease. Stability of these lysosomes in various media was estimated from measurements of proteolytic activity towards the ribonuclease, and of ribonuclease retention in particles. The lysosomes were stable at 37 degrees C in isotonic, sucrose-free solutions of KCl, NaCl, and potassium acetate, and in mixtures of these with MgCl2, showing that these salts are relatively impermeant through the lysosomal membranes. The membranes were less permeable to Na+ than to K+. Both KCl and NaCl exerted their optimal protective effects over a broad concentration range above 0.125 M in 0.025 M acetate buffer. Mg2+ enhanced the protective effect of both K4 and Na+; the osmotic effect of 0.075 M NaC1-0.05 M MgCl2 was indistinguishable during the entire course of ribonuclease digestion from that of isotonic sucrose. Osmotic protection by KC1-MgC12 was demonstrated over the H range5.5-7.0. A marked alteration in membrane properties occurs at lower temperatures in 0.11 M KC1-0.01 M MgCl2 such that, at 0 degrees C, K+ permeability is much higher than at 37 degrees C, as shown by a several-fold decrease in stability at the lower temperature.
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PMID:A thermally induced alteration in lysosome membranes: salt permeability at 0 and 37 degrees C. 23 78

Atypical eukaryotic RNA polymerase activity was demonstrated in nuclei of Crypthecodinium cohnii, a eukaryote devoid of histones. Nuclei were isolated from growing cultures of this dinoflagellate and assayed for endogenous RNA polymerase (EC 2.7.7.6) activity. There was a biphasic response to Mg2+ with optima at approximately 0.01 and 0.02 M MgCl2, but in contrast to other eukaryotic RNA polymerases, this enzyme activity was inhibited by low MnCl2 concentrations. In the presence of 0.01 M MgCL2 the optimum (NH4)2SO4 concentration was 0.025 M, a concentration at which the nuclei were lysed. Incorporation of [3H]UMP into RNA was inhibited by actinomycin D and dependent on the presence of undergraded DNA, and the reaction product was sensitive to ribonuclease and KOH digestion. Omission of one or more ribonucleoside triphosphates greatly reduced the incorporation. Only a slight enhancement of RNA polymerase activity resulted from the addition of various amounts of native and denatured calf thymus DNA. Spermine caused a marked inhibition while spermidine had little effect on RNA synthesis in the nuclei. Under the optimum conditions described in the present paper the nuclei incorporated approximately 3 pmoles of [3H]UMP/microgram DNA at 25 C for 15 min, and approximately 80% of this activity was inhibited by the eukaryotic RNA polymerase II inhibitor, alpha-amanitin (20 micrograms/ml). A unique situation therefore exists in C. cohnii nuclei, in which absence of histones (a prokaryotic trait) is combined with alpha-amanitin-sensitive RNA polymerase activity (a eukaryotic trait).
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PMID:RNA synthesis in isolated nuclei of the dinoflagellate Crypthecodinium cohnii. 57 93

The investigation of fluorescence and light-scattering change of histone F2a, ribonuclease, tyrosine, N-acetyltirosinamide, methyl ether tyrosine by the concentration increasing of NaCl, MgCl2, Na2SO4 in the surrounding medium was carried out. In the case of used salts the changes of tertiary structure and histones aggregations depend on the anion type, which is presented in the environment. The tertiary structure of histones formed in the presence of salt is stabilized by weak (hydrophobic and hydrogenic) interactions.
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PMID:[Structure and aggregation of histones. I. Influence of the ionic composition of the medium on the structure and effectiveness of the intermolecular relationships of histone F2a (H2A+H4)]. 88

A mitochondrial endonuclease from Drosophila melanogaster embryos was purified to near homogeneity by successive fractionation with DEAE-cellulose and heparin--avidgel-F, followed by FPLC chromatography on mono S, Superose 12 and a second mono S column. This enzyme digests double-stranded DNA more efficiently than heat-denatured DNA. The endonuclease activity has a molecular mass of 44 kDa, as determined under native conditions using a gel-filtration Superose 12 column. The prominent peptide detected by SDS/polyacrylamide gel electrophoresis likewise has a molecular mass of 44 kDa, suggesting a monomeric protein. The enzyme has an absolute requirement for divalent cations, preferring Mg2+ over Mn2+. No activity could be detected when these cations were replaced by Ca2+ or Zn2+. The pH optimum for this enzyme activity is 6.5-7.4 and its isoelectric point is 4.9. Both single-strand and double-strand breaks are introduced simultaneously into a supercoiled substrate in the presence of MgCl2 or MnCl2. Endonuclease-treated DNA serves as a substrate for DNA polymerase I from Escherichia coli, suggesting that 3'-OH termini are generated during cleavage. The enzyme is free from any detectable DNA exonuclease activity but not from RNase activity. Partial inhibition by antibodies raised against mitochondrial endonucleases derived from bovine heart and Saccharomyces cerevisiae have revealed a potential structural homology between these nucleases.
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PMID:Purification and characterization of a mitochondrial endonuclease from Drosophila melanogaster embryos. 133 52

Cell-free extracts employed as chromatin assembly systems contain a myriad of proteins, polyanions and nucleic acids. The roles of ATP, MgCl2 and other cofactors in the catalysis of nucleosome formation by the Xenopus laevis oocyte S-150 have yet to be established unequivocally. In this study we examine the influence of RNA in the assembly process. Under reaction conditions that inhibit nucleosome formation (+ EDTA), pretreatment of the extract with RNase A revives the chromatin assembly machinery while the rate of DNA supercoiling is stimulated significantly. Addition of purified RNA blocks DNA supercoiling. Taken together, these data suggest that the parameters surrounding in vitro chromatin assembly are variable and subject to modulation by endogenous factors.
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PMID:In vitro chromatin assembly promoted by the Xenopus laevis S-150 cell-free extract is enhanced by treatment with RNase A. 137 70

Rat liver ribonuclease P was isolated from a cytosolic fraction and shown to have optimal activity in the presence of 1 mM MgCl2 and 150-200 mM KCl using Escherchia coli pre-tRNA(Tyr) as substrate. In cesium sulfate isopycnic density gradients, the enzyme had a buoyant density of 1.36 g/ml, indicating that it is a ribonucleoprotein complex. Analysis of the RNAs in the enzyme sample purified through two successive Cs2SO4 density gradient steps revealed the copurification of two major species of RNA (RRP1 and RRP2) along with several less abundant RNAs. Rat liver ribonuclease P activity was insensitive to micrococcal nuclease pretreatment. However, the nuclease-treated preparations contained several incompletely degraded RNA species that may have been sufficient to support the ribonuclease P activity. When RNase A was substituted for micrococcal nuclease, the ribonuclease P activity was diminished by greater than 90%, suggesting the requirement for an RNA subunit for activity.
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PMID:Characterization of ribonuclease P isolated from rat liver cytosol. 160 34

We have used enzymic digestion as a structural probe to investigate components of the nuclear envelope of germinal vesicles from Xenopus oocytes. Previous studies have shown that these envelopes are composed of a double membrane in which nuclear pore complexes are embedded. The nuclear pore complexes are linked to a fibrous lamina that underlies the nucleoplasmic face of the envelope. The pores are also linked by pore-connecting fibrils that attach near their cytoplasmic face. Xenopus oocyte nuclear envelopes were remarkably resistant to extraction with salt solutions and, even after treatment with 1 M NaCl or 3 M MgCl2, pores, lamina and pore-connecting fibrils remained intact. However, mild proteolysis with trypsin selectively removed the lamina fibres from Triton-extracted nuclear envelopes to leave only the pore complexes and connecting fibrils. This observation confirmed that the pore-connecting fibrils were different from the lamina fibres and were probably constructed from different proteins. Trypsin digestion followed by Triton treatment resulted in the complete disintegration of the nuclear envelope, providing direct evidence for a structural role for the lamina in maintaining envelope integrity. Digestion with ribonuclease did not produce any marked change in the structure of Triton-extracted nuclear envelopes, indicating that probably neither the pore-connecting fibrils nor the cytoplasmic granules on the pore complexes contained a substantial proportion of RNA that was vital for their structural integrity.
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PMID:Selective digestion of nuclear envelopes from Xenopus oocyte germinal vesicles: possible structural role for the nuclear lamina. 170 42

The incorporation of 2'-fluoro- and 2'-aminonucleotides into a hammerhead ribozyme was accomplished by automated chemical synthesis. The presence of 2'-fluorouridines, 2'-fluorocytidines, or 2'-aminouridines did not appreciably decrease catalytic efficiency. Incorporation of 2'-aminocytidines decreased ribozyme activity approximately by a factor of 20. The replacement of all adenosines with 2'-fluoroadenosines abolished catalysis in the presence of MgCl2 within the limits of detection, but some activity was retained in the presence of MnCl2. This effect on catalysis was localized to a specific group of adenines within the conserved single-stranded region of the ribozyme. The decrease in catalytic efficiency was caused by a decrease in the rate constant; the Michaelis constant was unaltered. The 2'-fluoro and 2'-amino modifications conferred resistance toward ribonuclease degradation. Ribozymes containing 2'-fluoro- or 2'-aminonucleotides at all uridine and cytidine positions were stabilized against degradation in rabbit serum by a factor of at least 10(3) compared to unmodified ribozyme.
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PMID:Kinetic characterization of ribonuclease-resistant 2'-modified hammerhead ribozymes. 185 67


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