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:3.1.27.4 (ribonuclease)
6,621 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

RNase T, a nuclease thought to be involved in end-turnover of tRNA, has been purified about 4,000-fold from extracts of Escherichia coli. At this stage of purification, the enzyme was judged to be at least 95% pure based on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The native molecular weight of RNase T determined from gel filtration and sedimentation analyses is about 50,000, whereas the monomer molecular weight determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis is 25,000, suggesting that the protein is an alpha 2 dimer. Purified RNase T is extremely sensitive to inactivation by oxidation, sulfhydryl group reagents, and temperature. The ribonuclease activity against tRNA-C-C-[14C]A is optimal at pH 8-9 in the presence of 2-5 mM MgCl2 and ionic strengths of less than 50mM. Although RNase T is highly specific for intact tRNA-C-C-A as a substrate and can hydrolyze all species in a mixed population of tRNA, it is inhibited by other RNAs, such as poly(A), rRNA, 5 S RNA, and tRNA-C-C. RNase T is an exoribonuclease which initiates attack at a free 3' terminus of tRNA and releases AMP; aminoacyl-tRNA is not a substrate. The role of RNase T in the end-turnover of tRNA and its possible involvement in other aspects of RNA metabolism are discussed.
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PMID:Purification and characterization of Escherichia coli RNase T. 388 94

Sterile, concentrated culture supernatant from Pasteurella haemolytica (biotype A, serotype 1) strain 630 was subjected to physical, chemical, and immunologic treatments to determine their influence on leukotoxin (cytotoxin) activity contained in the supernatant. Each treated sample contained approximately 8 chemiluminescence inhibitory units of leukotoxin. Treatment effects were evaluated for their ability to inactivate leukotoxin activity. Leukotoxin activity in treated samples was determined by inhibition of the luminol-dependent chemiluminescence response of bovine neutrophils. Optimal leukotoxin synthesis by P haemolytica occurred when the bacteria were at the logarithmic growth phase, whereas stationary phase cultures contained minimal amounts of leukotoxin activity in their culture supernatant. Leukotoxin activity was heat labile; activity was substantially decreased when concentrated culture supernatant samples containing leukotoxin activity were incubated at 37 C for several hours. When concentrated culture supernatant was incubated at progressively decreasing temperatures, there was a progressive increase in the length of time that the leukotoxin retained its biologic activity. Samples stored at -70 C retained activity for at least 2 months. Leukotoxin activity was nondialyzable and was able to withstand considerable extremes in hydrogen ion concentration. Leukotoxin activity could not be pelleted when subjected to forces of 100,000 X g for 1 hour. Chemical and enzymatic studies suggested that P haemolytica leukotoxin contained carbohydrate and protein moieties. Chemical treatment with 0.2% sodium lauryl sulfate, 0.5% sodium deoxycholate, 7.5 mM EDTA and 8M urea with 8 mM 2-mercaptoethanol and enzymatic treatment with lipase, ribonuclease, and deoxyribonuclease had no discernible effect on leukotoxin activity.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Pasteurella haemolytica leukotoxin: physicochemical characteristics and susceptibility of leukotoxin to enzymatic treatment. 396 75

The means by which coxsackievirus type A9 (CA9) is inactivated by proteolytic enzymes was investigated. After reaction of (14)C-leucine-labeled CA9 with Pronase, free leucine was liberated as measured by radiochromatography. Treatment of (14)C-leucine-labeled CA9 with trypsin or proteolytic filtrates of Pseudomonas aeruginosa caused the release of a variety of labeled substances. The extent of viral ribonucleic acid (RNA) release after exposure of CA9 to Pronase was determined by RNA infectivity tests or trichloroacetic acid solubility tests. Infective viral RNA was found not to be consistently released by reaction of CA9 with Pronase, but further treatment with 1% sodium dodecyl sulfate at pH 7.0 promoted viral RNA release. Sodium dodecyl sulfate treatment of CA9 that had not been reacted with Pronase did not inactivate virus or cause viral RNA release. Reaction of Pronase with (32)P-labeled CA9 resulted in the liberation of virus components soluble in cold trichloroacetic acid, whereas untreated CA9 or CA9 reacted with ribonuclease were precipitated by cold trichloroacetic acid. These results demonstrate that the primary means by which protease-sensitive enteroviruses are inactivated is by degradation of the virus capsid, with subsequent release of viral RNA.
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PMID:Degradation of coxsackievirus type A9 by proteolytic enzymes. 420 58

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

The foot-and-mouth disease virus RNA polymerase complex was dissociated from cellular membranes with deoxycholate in the presence of dextran sulfate. The soluble polymerase complex was active in the cell-free synthesis of virus-specific RNA; solubilization of the complex permitted direct analysis of the cell-free reaction mixtures without recourse to RNA extraction. A major RNA-containing component found early during cell-free incubation ranged from approximately 140 to 300S. The final major products of the cell-free system were 37S virus RNA, 20S ribonuclease-resistant RNA, and a 50S component containing RNA.
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PMID:Detergent-solubilized RNA polymerase from cells infected with foot-and-mouth disease virus. 429 91

After the attachment of radioactive coxsackievirus B3 to HeLa cells at 0 C and subsequent incubation at 37 C, 50 to 80% of attached virus radioactivity was eluted from the cells within 1 hr. Eluted virus had a buoyant density of 1.21 in a potassium tartrate gradient, sedimented more slowly than native virus in sucrose gradients, was resistant to ribonuclease, was unstable in CsCl centrifugation, and did not reattach to uninfected cells. Electrophoretic studies of sodium dodecyl sulfate-disrupted B3 virus in sodium dodecyl sulfate-polyacrylamide gels revealed four radioactive virus polypeptides (VP 1 to 4), of which the three largest migrated slightly faster than their poliovirus T1 counterparts. In contrast, electrophoretic analysis of eluted virus, after banding in a tartrate gradient or pelleting by centrifugation, showed the absence of the fastest migrating polypeptide, VP 4. VP 4 was recovered in the supernatant fluid when the eluted virions were removed by high-speed centrifugation. The results indicate that VP 4 is located at the surface of the native virion, and its dissociation from the capsid may represent the first specific alteration of the virion after virus-receptor interaction at the cell surface.
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PMID:Specific alterations of coxsackievirus B3 eluted from HeLa cells. 433 54

Poliovirus-infected cells contain a previously unrecognized particle which appears to be an intermediate in virion synthesis and therefore has been named proviron. It sediments at about 125S, contains the three procapsid proteins, VP-0, VP-1, and VP-3, and has 35S viral RNA. It is disrupted both by sodium dodecyl sulfate and EDTA but the RNA resists digestion by ribonuclease. Pulsechase experiments and studies employing the virus-specific inhibitor, guanidine, all indicate that the proviron is formed by combination of newly made RNA with the procapsid. Cleavage of VP-0 to form VP-2 and VP-4 follows formation of the provirion and would be the final step in poliovirus morphogenesis.
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PMID:Morphogenesis of poliovirus. II. Demonstration of a new intermediate, the proviron. 435 64

A Mycoplasma gallisepticum subcellular fraction (P2), which contains the deoxyribonucleic acid replication complex, can be isolated by differential centrifugation of freeze-thaw-lysed cells. The nascent deoxyribonucleic acid is released from P2 by Lubrol-WX, sodium dodecyl sulfate, Pronase, and deoxyribonuclease, but not by saponin, ribonuclease, phospholipase C, or high-frequency sonic treatment. Sonic treatment further fractionates the cell ghost and allows partial purification, on sucrose density gradients, of a deoxyribonucleic acid replication complex attached to the cells' polar membrane-bleb-infrableb structures.
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PMID:Partial purification of a membrane-associated deoxyribonucleic acid complex from Mycoplasma gallisepticum. 442 Sep 60

A structure consisting of poly(A) complexed with other components is released from polysomes by ribonuclease treatment. The poly(A) complex has a sedimentation value of 12-15, while the corresponding sedimentation value for free poly(A) is 4. The complex does not appear to represent an artifact formed by interaction of free poly(A) with either cytoplasmic or polysomal proteins. The polynucleotide released from the complex by treatment with sodium dodecyl sulfate shows the same electrophoretic mobility as that of poly(A) isolated from deproteinized polysomal RNA. The poly(A) in the complex is partially protected from digestion by T(2) ribonuclease. At least part of the poly(A) is available for base pairing with poly(U). The components associated with the poly(A) cause it to bind to Millipore filters at low ionic strength. These components are removed from the complex by Pronase digestion. The findings indicate that the poly(A) segment in messenger RNA serves as a binding site for a particle. This particle appears to consist of proteins.
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PMID:A particle associated with the polyadenylate segment in mammalian messenger RNA. 450 17

An electron microscopy study has been made of the effects of dissolution of the plasma membrane of Escherichia coli with sodium dodecyl sulfate (SDS) on the organization of the nucleoplasm and the cytoplasm. The alterations observed in time course experiments were related to absorbance changes and to release of macromolecules from the cells. As the cells became plasmolyzed, under the conditions used, the first visible effect of SDS was a collapse of the plasmolysis spaces. This was accompanied by a displacement of the nuclear material which then appeared in broad contact with the redeployed plasma membrane. This initial displacement of nuclear material to the cell border may indicate an association between the nucleoplasm and the plasma membrane. Upon further dissolution of the plasma membrane, the nuclear material receded from the cell margin and contracted into an axial filament. Meanwhile, the cytoplasm dissociated into an amorphous, Pronase-sensitive component and an electron-opaque, granular one sensitive to ribonuclease. The latter represented one continuous area of ribosomal structures surrounding the nucleoplasm, an organization which did not occur when the cells were inhibited with rifamycin before SDS treatment. During prolonged SDS interaction, approximately 65% of the cellular protein, 25% of the ribonucleic acid and 40% of the deoxyribonucleic acid were released from the cells concomitant with the disappearance of the amorphous cytoplasmic part, expansion of the ribosomal aggregate, and rearrangement of the nuclear material at the cell periphery. The observations support the contention that all ribosomal structures bear a direct relationship with the nucleoplasm.
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PMID:Effects of treatment with sodium dodecyl sulfate on the ultrastructure of Escherichia coli. 455 30


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