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)

Isoenzymatic forms alpha 2, alpha beta, and beta 2 of bovine seminal ribonuclease are generated by the transformation of beta-type into alpha-type subunit through deamidation of a single amide group [Di Donato, A., & D'Alessio, G. (1981) Biochemistry 20, 7232-7237]. The residue involved in this selective deamidation has been identified as Asn67. Deamidation occurs by formation of a cyclic imide intermediate involving the Gly at position 68. Opening of the cyclic imide may occur on either side of the nitrogen, generating both the normal alpha-aspartyl and an isoaspartyl residue at position 67. The alpha-carboxyl of the isoaspartyl residue is effectively methylated by bovine brain protein carboxylmethyltransferase.
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PMID:Selective deamidation and enzymatic methylation of seminal ribonuclease. 382 85

Purification of progenitor toxin of Clostridium botulinum type B strain Okra was undertaken by sequential steps of acid precipitation, extraction, ammonium sulfate precipitation, ribonuclease digestion, acid precipitation, protamine treatment, sulphopropyl-Sephadex chromatography, and Sephadex G-200 gel filtration. Two different molecular-sized toxins, named large (L) and medium (M) toxins, were obtained. L toxin was centrifugally homogeneous but electrophoretically heterogeneous. It contained 2.5 x 10(8) to 3.0 x 10(8) mean lethal doses per mg of nitrogen, and its sedimentation constant was 16S. M toxin was centrifugally and electrophoretically homogeneous. It contained 5.5 x 10(8) to 6.0 x 10(8) mean lethal doses per mg of nitrogen, and its sedimentation constant was 12S. The presence of both L and M toxins in spent culture was demonstrated. It seems justified, therefore, to call both progenitor toxins. Both consisted of toxic and nontoxic components. The toxic components of L and M toxins appeared to be identical with each other. The nontoxic component of L toxin was 12S and possessed a hemagglutinin activity of about 0.5% that of type A crystalline toxin; that of M toxin was 7S and possessed no hemagglutinin activity. They were antigenically related but not identical.
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PMID:Purification and some properties of progenitor toxins of Clostridium botulinum type B. 421 81

Synthesis of extracellular ribonuclease is induced in cell cultures of Ustilago sphaerogena that are starved for nitrogen and exposed to the gratuitous inducer, 6-mercaptopurine. Cesium, ammonium, or alkylammonium ion represses ribonuclease induction. Addition of citric-acid cycle intermediates to cesium ionrepressed cultures partially restores the rate of ribonuclease synthesis to the induced level. Enzymes involved in assimilation of nitrogen from different sources are also repressed by cesium ion and derepressed by intermediates from the citric acid cycle.
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PMID:Control by cesium and intermediates of the citric acid cycle of extracellular ribonuclease and other enzymes involved in the assimilation of nitrogen. 528 82

The substrate specificity of pancreatic ribonuclease A is discussed in light of observations based on accurate X-ray structure analysis of several enzyme-nucleotide complexes. A hypothesis for protein-nucleic acid recognition is presented which proposes that: (a) pyrimidine bases in RNA are recognised by ribonuclease due to the charge complementarity of two groups (the amide nitrogen and the side chain oxygen (OG) of threonine 45) of the protein and relevant atoms in the heterocyclic base (O2 and N3 in pyrimidine nucleotides); (b) interaction of the protein with the ribose moiety of the nucleotides is non-specific; and (c) conformational flexibility in the region of the scissile P-O bond is provided by different locations of the phosphoryl oxygens, rather than by an overall translation of the phosphate moiety.
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PMID:Enzyme specificity: base recognition and hydrolysis of RNA by ribonuclease A. 619 18

Insulin, ribonuclease, papain and collagen solutions saturated with nitrogen, N2O or air were irradiated with doses of 10 to 640 Gy of gamma rays. Protein solutions were also oxidized enzymatically in a system of horse-radish peroxidase: hydrogen peroxide. Column chromatography (Sephadex G-75 or Sephacryl S-200) of treated protein solutions revealed that they contain protein molecular aggregates. Nitrogen saturation of solution before irradiation was most favourable for radiation-induced aggregation of proteins. Fluorescence analysis of protein solutions resulted in detection of dityrosyl structures in irradiated as well as in enzymatically oxidized proteins. Concentration of dityrosine in proteins studied was determined fluorimetrically in their hydrolysates separated on BioGel P-2 column. In irradiated proteins, dityrosine was present almost exclusively in their aggregated forms. In proteins oxidized enzymatically, dityrosine was also present in fractions containing apparently unchanged protein. Mechanisms which could account for differences in the yield of dityrosine formation in radiolysis and in enzymatic oxidation of proteins are suggested.
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PMID:Radiolytic and enzymatic dimerization of tyrosyl residues in insulin, ribonuclease, papain and collagen. 633 34

A double-stranded ribonuclease has been purified more than 90-fold to near homogeneity from the yeast, Saccharomyces cerevisiae. The enzyme shows a high specificity for double-stranded RNA as its substrate. It has a molecular weight of 27000 as determined by sodium dodecyl sulphate/polyacrylamide gel electrophoresis. The enzyme degrades dsRNA optimally at 30 degrees C; it is stimulated by KCl and by the -SH reagent, dithiothreitol. In contrast to RNase III from Escherichia coli, the yeast enzyme is inhibited by divalent cations. Physiological studies have demonstrated that in vivo levels of the enzyme activity fell during the latter part of the exponential growth phase but rose during stationary phase. The specific activity of the enzyme in nitrogen-starved yeast cells was 2-3-fold higher than in non-starved cells. The enzyme could be detected in yeast strains containing both, one or none of the species of cytoplasmic dsRNA (L and MdsRNAs) and may, therefore, have some wider role.
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PMID:Purification and properties of a double-stranded ribonuclease from the yeast Saccharomyces cerevisiae. 636 60

Mammary gland polysomes are difficult to isolate from the lactating rat using methods developed for other species and tissues, most likely due to high calcium-stimulated ribonuclease activity in that tissue. A new method, utilizing ethyleneglycol-bis-(beta-aminoethylether)-N,N'-tetraacetic acid (EGTA) to bind calcium, yields highly aggregated polysomes from lactating rat mammary gland. Fresh mammary tissue is pulverized under liquid nitrogen. Free and membrane-bound polysomes are isolated by differential centrifugation in solutions containing 100 mM KCl, 100 mM MgCl2, 75 mM EGTA, 500 micrograms/ml heparin and 50 mM Tris buffer, pH 8.2 at 5 degrees C. Bound polysomes are released from the endoplasmic reticulum using Triton X-100 and deoxycholate. Polysome profiles are obtained on linear sucrose gradients and scanned at 254 nm. The method gives quantitative recovery of homogenate total RNA. To demonstrate that the method can be used to study nutritional effects on mammary gland polysome aggregation, lactating rats were fasted 22-66 h and then refed a stock diet for 71-95 h. Refeeding increased the percentage of polysomes (trimers or larger) in the bound fraction from 84 +/- 1 to 93 +/- 1% (P less than 0.001) and in the free fraction from 42 +/- 2 to 55 +/- 3% (P less than 0.001).
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PMID:A method for isolation of undegraded free and membrane-bound ribosomes from rat lactating mammary gland. 642 19

The effects of different intravenous nutritional regimens on a number of biochemical indices of nutritional status were studied during the 8-day period following severe trauma. The inclusion of large amounts of amino acids (high nitrogen (N) was shown to greatly improve N balance over an isocaloric regimen containing no amino acids (O g N). The concentration of serum albumin, transferrin, prealbumin, and retinol-binding protein all fell during the study period in both patient groups, whereas the serum concentrations of acute phase reactants and of ribonuclease increased in the two groups. The sum of plasma levels of branched-chain amino acids and the essential amino acids was increased to a greater extent in the high N group. These amino acid totals and the ratio of glycine/valine showed a significant correlation with N balance in this group. Despite the marked difference in N balance, 3-methylhistidine excretion was increased but equal in the two nutritional groups, suggesting an increased rate of muscle protein breakdown in both groups, which appears not to be influenced by amino acid nutrition. It is concluded that N balance can be significantly improved in the immediate posttrauma period by provision of amino acids together with energy substrates. None of the biochemical variables measured, with the exception of plasma levels of essential amino acids, reflected these marked differences in N balance.
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PMID:Biochemical changes associated with severe trauma. 677 18

When cells of the yeast, Saccharomyces cerevisiae, were deprived of nitrogen, a condition leading to G1 arrest, there was an immediate increase in the levels of total ribonuclease (RNase) activity within these cells. During starvation, only the cells arrested in G1 showed increased RNase activity. Although the RNase activities of extracts of starved and actively growing cells were similarly influenced by pH, the activities of starved cells were less stable on both storage and heating. Differences were also noted in substrate specificity. The results of this study suggest that arrest within G1 may increase RNase activity. However, all RNases did not appear to be influenced equally, since the total pool of RNase activity from log phase and G1 arrested cells showed differences in stability and substrate specificity.
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PMID:Ribonuclease activity during G1 arrest of the yeast Saccharomyces cerevisiae. 698 36

Combined action of polyornithine and lecithin modified tobacco mosaic virus (TMV) virions making them sensitive to ribonuclease (RNase), pronase or Triton X-100. Sedimentational analysis and examination of the fluorescence spectrum revealed that the reaction product obtained after RNase treatments of modified TMV was a three-component complex made of coat protein, polyornithine and lecithin. The minimum requirement for the modification was completely fulfilled by cetyltrimethylammonium bromide, suggesting that a positively charged nitrogen group and an alkyl group of moderate size, C10--18, are necessary components. These components react with the surface region of TMV which is considered to have an important role in connecting coat protein subunits in TMV virions.
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PMID:Modification of tobacco mosaic virus by polyornithine and lecithin. 741 96


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