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)

The size distribution of newly synthesized and old poly(A) sequences on transcripts of the giant tissue specific puffs, Balbiani rings in salivary glands of Chironomus tentans has been determined. After labeling with [3H]adenosine, poly(A) containing Balbiani ring RNA(75S RNA) was selectively collected by means of a recently developed technique. This combines electrophoretic fractionation and affinity chromatography in one run by insertion of poly(U) immobilized in glass fiber filters in an agarose gel slab. The majority of short-term labeled poly(A) chains released from poly(A) containing 75S RNA molecules is distributed within a narrow size range migrating as one peak with a mean value of 103 +/- 2 nucleotides, which is probably the initial length of poly(A). The labeling pattern of ribonuclease resistant poly(A) stretches after chase with unlabeled adenosine displays a relatively broad and heterogeneous size spectrum from at least 20 to more than 100 nucleotides. The main peak of labeled adenylate core in newly formed poly(A) containing RNA of non-Balbiani ring origin is dispersed within a broader size range than that of Balbiani ring RNA and possesses an average value of 94 +/- 2 nucleotides. During chase conditions, the relative frequency of occurrence of poly(A) chains of 75S RNA in the size range of 100 nucleotides exhibits a significant decrease in parallel with a rather uniform gain in the size classes between 20--50 nucleotides. However, the results are inconsistent with the existence of an age-dependent shortening of poly(A) chains in the balbiani ring RNA. A significant portion of 75S RNA molecules remain associated with poly(A) segments which are essentially of original size even after 21 hr in the presence of unlabeled adenosine. This finding provides support for the possibility that the initiation of the poly(A) shortening in 75S RNA is a stochastic process.
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PMID:The size distribution of poly(A) in newly synthesized and old Balbiani ring RNA. 46 Jan 78

Undegraded rat liver polysomes were obtained after homogenizing the tissue in a medium containing NH4Cl, heparine, and yeast tRNA. Purification of poly(A)-containing RNA from polysomal RNA was accomplished by affinity chromatography on oligo(dT)-cellulose columns. Poly(A)-containing RNA molecules were monitored by the formation of ribonuclease-resistant hybrids with [3H]poly(U). To improve the separation of messenger RNA and ribosomal RNA by oligo(dT)-cellulose it was found essential to dissociate the aggregates formed between both molecular species by heat treatment in the presence of dimethylsulfoxide (Me2SO) prior to chromatography. Sucrose gradient analysis under denaturing conditions showed that the preparations obtained were virtually free of ribosomal RNA. Poly(A)-containing RNA constituted approx. 2.2% of the total polysomal RNA and the number average size was 1500--1800 nucleotides, as judged by sedimentation analysis on sucrose density gradients containing Me2SO. Approximately 8.2% of the purified preparation obtained was able to anneal with [3H]poly(U); the number average nucleotide length of the poly(A) segment of the RNA population was calculated to be 133 adenylate residues. Based on these values, our preparations appear to be greater than 90% pure. The RNA fractions obtained after oligo(dT)-cellulose chromatography were used to direct the synthesis of liver polypeptides in a heterologous cell-free system derived from wheat-germ. The system was optimized with respect to monovalent and divalent cations, and presence of polyamines (spermine). More than 65% of the translational activity present in the unfractionated polysomal RNA was recovered in the final poly(A)-containing RNA fraction. However, about 25% of the activity was found to be associated with the unbound fraction which was essentially free of poly(A)-containing RNA. Immunoprecipitation analysis with a specific antiserum to rat serum albumin demonstrated that about 6--8% of the labeled synthetic products translated from the poly(A)-containing RNA sample corresponded to serum albumin. Analysis of the translation products by sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed a heterogeneous distribution of molecular sizes ranging from 15 000 to greater than 70 000 daltons. Spermine not only increased the overall yield and extent of protein synthesis, but also resulted in higher yields of large protein products. Under optimal translation conditions a discrete peak representing about 7% of the total radioactivity was observed to migrate with rat serum albumin.
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PMID:Isolation and characterization of poly(adenylic acid)-containing messenger ribonucleic acid from rat liver polysomes. 66 61

1. The interaction of ribonuclease U-2 (RNAase U-2) with its substrate analogues has been investigated by a gel filtration method. At pH 4.5 and 30 degrees C, the apparent binding strength of the substrate analogues was in the following order; adenylate greater than guanylate greater than inosylate greater than cytidylate among 2'-nucleotides and 2'- greater than 3'- greater than 5'- among adenylate isomers. The formation of an equimolar complex of RNAase U-2 and 2'-nucleotide was indicated from the Scatchard plot. 2. The interaction of RNAase U-2 with 2'-adenylate or 2'-guanylate was observed spectrophotometrically. The complex of RNAase U-2 and 2'-adenylate yielded not only an absorption difference spectrum having a broad positive peak at 280 to 285 nm and a negative trough at 256 nm but also a circular dichroic difference spectrum having a positive peak at around 250 nm and a negative trough at around 290 nm. The complex of RNAase U-2 and 2'-guanylate gave a similar difference spectrum to that of the RNAase T-1 - 3'-guanylate complex, in absorption as well as in circular dichroism.
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PMID:On the interaction of ribonuclease U-2 and substrate analogues. 112 Jan 63

Rapidly labelled high molecular weight nuclear RNA from lymphocytes of chronic lymphocytic leukaemia was analysed for ribonuclease-stable adenylate-rich and double-stranded regions. The polyadenylate content corresponds to 0.4-0.5 percent and the content of double-stranded sequences to 2-4 percent of the total nucleotides. Partial association of polyadenylate segments with double-stranded regions was found by comparative analysis of (3H)-adenosine and (3H)-uridine labelled ribonuclease-stable RNA before and after thermal denaturation. Comparison with normal lymphocytes shows lower proportions of polyadenylate-containing RNA binding to poly(U)-Sepharose in leukaemia cells than in normals. Partial degradation of rapidly labelled high molecular weight RNA was found in leukaemia cases with low white cell counts.
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PMID:Heterogeneous nuclear rna from lymphocytes of chronic lymphocytic leukaemia: adenylate-rich and double-stranded regions. 112 45

Preparative agarose gel electrophoresis under denaturing conditions has been successfully employed to purify large quantities of ovalbumin mRNA from hen oviducts. The mRNA thus prepared is physically homogeneous based on its migration as a single component on electrophoresis in both analytical acid-urea agarose gels and formamide-containing, neutral polyacrylaminde gels; it also sediments as a single peak in sucrose gradients containing 70% formamide. The mRNA is chemically free of ribosomal RNA contamination since its oligonucleotide fingerprint map after complete T1 ribonuclease digestion contains no detectable specific large oligonucleotide markers of ribosomal RNAs. It is also not contaminated by other biologically active messenger RNAs because, when it is added to the cell-free wheat germ translation system, the only protein product synthesized is ovalbumin as analyzed by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate and specific immunoprecipitation. Ovalbumin mRNA has a nucleotide composition of 32.3% A, 21.0% G, 25.7% U, and 20.7% C [(A+U)/(G+C) equal 1.41]. The mRNA contains a heterogeneous poly(A) tract ranging from 20 to 140 residues with a number average chain length of 62 adenylate residues. The molecular weight of the sodium salt of the purified mRNA is approximately 650,000 +/- 63,000, corresponding to a chain length of 1890 +/- 180 nucleotides, as determined by electron microscopy under completely denaturing conditions. This value is in close agreement with the values obtained from: (a) sucrose gradient centrifugation in the presence of 70% formamide; (b) evaluation of poly(A) content in the mRNA and the number average chain length of its poly(A) tract; and (c) sedimentation velocity studies in the presence of 3% formaldehyde. When 125I-labeled ovalbumin mRNA is allowed to hybridize with a large excess of chick DNA, the observed kinetics of hybridization reveal no appreciable reaction between the mRNA and the repeated sequences of the chick DNA, although the mRNA appears to be approximately 600 nucleotides longer than necessary to code for ovalbumin. It thus appears that the entire ovalbumin mRNA is primarily transcribed from a unique sequence in the chick genome.
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PMID:Physical and chemical characterization of purified ovalbumin messenger RNA. 115 96

Evidence is presented from three experimental systems to support the allosteric model of Walker et al. (1975) (Biochem. J. 147, 425-433) which explains the substrate-concentration-dependent transition observed in the RNAase (ribonuclease)-catalysed hydrolysis of 2':3'-cyclic CMP (cytidine 2':3'-cyclic monophosphate). 1. Kinetic studies of the initial rate of hydrolysis of 2':3'-cyclic CMP show that the midpoint of the transition shifts to lower concentrations of 2':3'-cyclic CMP in the presence of the substrate analogues 3'-CMP, 5'-CMP, 3'-AMP, 3'-UMP and Pi; 2'-CMP and 2'-UMP do not cause such a shift. 2. Trypsin-digestion studies show that a conformational change in RNAase to a form less susceptible to tryptic inactivation is induced in the presence of the substrate analogues 3'-CMP, 5'-CMP, 3'-AMP, and 3'-UMP. 2'-CMP, 2'-AMP and 2'-UMP do not induce this conformational change. 3. Equilibrium-dialysis experiments demonstrate the multiple binding of molecules of 3'-CMP, 3'-AMP and 5'-AMP to a molecule of RNAase. 2'-CMP binds the ratio 1:1 over the analogue concentration range studied.
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PMID:Further evidence for an allosteric model for ribonuclease. 127 91

To assess whether myoglobin adversely affects renal adenylate pools, rats were infused with purified myoglobin (50 mg/100 g body wt) for two hours and renal ATP, ADP, and AMP levels were measured in the absence of shock, after 25 minutes of hemorrhagic shock (55 to 60 mm Hg) or 30 minutes post-recovery. In the absence of shock, myoglobin lowered ATP by 24% (assessed 65 min post-infusion) without affecting renal blood flow (RBF). This effect was completely blocked by deferoxamine (DFO) treatment and it could not be reproduced by ribonuclease infusion (a non-Fe containing, but filtered, protein). Myoglobin + shock caused a three- to fourfold greater decline in ATP than did shock alone despite comparable RBFs. Shock plus myoglobin, but neither one alone, induced substantial S1/S2 proximal tubular morphologic damage and a severe reduction in creatinine clearance, confirming synergistic injury. Ribonuclease completely reproduced myoglobin's effect on shock-induced adenylate profiles. DFO +/- hydroxyl radical scavenger therapy (Na benzoate) did not block the myoglobin shock effect on adenylate pools. Post-shock adenylate recovery was not compromised by myoglobin pre-treatment. If renal artery occlusion (RAO), rather than shock, was used as the ischemic challenge, myoglobin had no discernible impact on adenine nucleotide content. This study concludes that: 1) myoglobin modestly lowers baseline adenylate pools due to an Fe dependent mechanism; 2) myoglobin drastically accentuates shock-induced adenylate depletion by a non-hemodynamic/non-Fe dependent mechanism; 3) myoglobin nephrotoxicity cannot be attributed solely to tissue iron loading; and 4) the RAO model can completely mask important influences on ischemic cellular energetics.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Myoglobin depletes renal adenine nucleotide pools in the presence and absence of shock. 200 25

The substrate specificity of a calcium-dependent endoribonuclease of Trypanosoma brucei cytoplasm has been further determined. The actions of the enzyme on transfer RNA, ribosomal RNA and various synthetic polyribonucleotides indicate that the enzyme degrades double-stranded as well as single-stranded RNAs; while it preferentially hydrolyses polyribonucleotides having adenylic acid residues, and has a pronounced preference for poly (adenylic acid). Its apparent Michaelis constant (Km) values using different substrates also suggest a base-preferential affinity of the enzyme to adenylate. The relative activity of the ribonuclease against homopolyribonucleotides is poly(A) greater than poly(U) greater than poly(C); while poly(G) is completely resistant to the activity. Poly(A) segments on poly(A)-rich RNA are selectively hydrolyzed by the endoribonuclease. A possible implication of this enzyme in the post-transcriptional modification and turnover of mRNA molecules is suggested.
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PMID:Calcium-dependent endoribonuclease of Trypanosoma brucei has a base-preferential affinity to adenylate. 258 76

The activity of the endoribonuclease VI from Artemia is sensitive to several purine nucleotides. The enzyme is non-competitively inhibited by diguanosine tetraphosphate (Ki = 75 microM), a nucleotide abundant in Artemia encysted gastrulae and located in the same particulate fraction as the gastrular ribonuclease. Diguanosine triphosphate and diadenosine tetraphosphate are less efficient inhibitors (Ki congruent to 200 microM). The ribonuclease is non-competitively inhibited by 5'-AMP (Ki = 10 microM) and 5'-GMP (Ki = 50 microM) but is insensitive to the corresponding 5'-phosphates of cytosine and uridine. Other purine mononucleotides inhibit the enzyme activity less efficiently. The modulation of the enzyme activity by these nucleotides is discussed in relation with the changes in ribonuclease activity during early development of Artemia.
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PMID:Diguanosine 5',5'''-P1,P4-tetraphosphate and other purine nucleotides inhibit endoribonuclease VI from Artemia. 341 43

1. The alanyl-s-RNA synthetase of tomato roots has been purified by ammonium sulphate precipitation, adsorption on calcium phosphate gel and DEAE-cellulose chromatography and its properties have been investigated. 2. Enzyme activity was measured by using the hydroxamate assay, the [(32)P]pyrophosphate-ATP-exchange assay and the [(14)C]alanyl-s-RNA assay. The purified enzyme was specific for l-alanine and was activated by Mg(2+) ions and to a smaller extent by Co(2+) and Mn(2+) ions. It was free from adenosine triphosphatase, pyrophosphatase and ribonuclease, and possessed a specific activity comparable with that of the most highly purified aminoacyl-s-RNA synthetases from animal and microbial systems. 3. The properties of the purified enzyme were similar in many respects to most other highly purified aminoacyl-s-RNA synthetases. It differed, however, in that the pH optimum of the hydroxamate assay was almost the same as that of the pyrophosphate-ATP-exchange assay and in requiring a high concentration of l-alanine for maximum activity (100mumoles/ml.). 4. The purified enzyme was not absolutely specific for tomato-root s-RNA; slight activity was also observed with yeast s-RNA. 5. The properties of this enzyme are fully consistent with the suggestion that the enzymic formation of alanyl-s-RNA proceeds via the intermediate formation of alanyl acyl-adenylate with the elimination of pyrophosphate from ATP. It remains to be shown the extent to which alanyl-s-RNA participates further in subsequent stages of protein synthesis in plants.
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PMID:The purification and properties of the alanyl-transfer ribonucleic acid synthetase of tomato roots. 428 91


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