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)

A procedure is described for the preparation of free and bound polysomes from whole homogenates of rat liver tissue. Liver is homogenized in a conventional medium containing glutathione; then after a 12-min centrifugation at 131000g, the free polysomes in the supernatant are saved, while the membrane-bound polysomes in the pellet are suspended in a mixture of ribonuclease inhibitors (cell sap, 250 mM KCl, and glutathione), homogenized in the presence of detergent (Triton X-100), centirfuged for 5 min at 1470g, decanted, and treated with deoxycholate; the polysomes in the two supernatants are harvested by centrifugation through sucrose gradients containing 250 mM KCl and cell sap. Free and bound polysomes prepared in this manner are undegraded, equally active in cell-free protein synthesis, and virtually free of ribonuclease, membranous material, glycogen, deoxycholate, completed protein, and cross-contamination. The recovery of polysomes is approximately 95% and the distribution between the free and membrane-bound state is 25 and 75%, respectively. The molecular weight profiles after sodium dodecyl sulfate-acrylamide gel electrophoresis of the polypeptides completed and released by free and bound polysomes in vitro are different, indicating that there are quantitative differences in the synthesis of various size polypeptides between the two polysome classes. The differential centrifugation procedure is rapid and reproducible, requires much less ultracentrifugation than the isopycnic technique, and provides a nearly quantitative means of separating free and bound polysomes.
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PMID:A procedure for the quantitative recovery of homogeneous populations of undegraded free and bound polysomes from rat liver. 126 92

A highly purified membrane preparation derived from the microsomal fraction of rat hepatocytes has been chemically characterized and fractionated by means of gel filtration. The preparation has been freed of ribosomes and intravesicular protein and has a composition on a w/w basis of 52.1% protein, 45.0% phospholipid, 2.9% carbohydrate and no RNA. 97 +/- 2% of the total membrane phosphorus is accounted for as phospholipid phosphorus. Determination of the molecular weight distribution of the constituent polypeptides by sodium dodecyl sulfate-polyacrylamide gel electrophoresis gave values ranging from 171 000 to 16 000 for the major classes of proteins. Although several membrane glycoproteins have been indentified, the most prominent species has an apparent molecular weight of 171 000, 40% of the total microsomal protein is present in the 49 000-60 000 molecular weight region. Examination of the intrinsic polypeptide composition of membranes obtained from smooth and degranulated rough endoplasmic reticulum revealed no detectable qualitative differences. Sodium dodecyl sulfate-solubilized microsomal membrane proteins were separated by gel filtration into much simplified molecular weight classes, some of which showed predominantly a single electrophoretic component. Amino acid analysis of individual fractions showed a noticeable trend toward a decreasing ratio of acidic to basic residues with decreasing molecular weight. Membrane phosphorus was distributed between two chromatographic fractions: one containing membrane phospholipid (97% of the total) as well as essentially all the cholesterol, the other, at the inclusion volume of the gel filtration system, containing small molecular weight species (3% of the total phosphorus). The absence of a ribonuclease-resistant RNA component eluting near the void volume clearly distinguishes the microsomal membrane from the nuclear envelope.
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PMID:Characterization of the membrane matrix derived from the microsomal fraction of rat hepatocytes. 127 22

We previously cloned, sequenced, and expressed two distinct mammalian Na+/H+ exchanger isoforms (NHE-1 and NHE-2). We report here the cloning of a composite cDNA which encodes a third mammalian isoform (NHE-3), which is expressed specifically in intestine and kidney. The protein deduced from the longest open reading frame of this composite sequence has 832 amino acids with a calculated Mr of 92,747. The hydrophobicity plot of NHE-3 is very similar to that of NHE-1 and NHE-2. NHE-3 is also predicted to have 10-12 membrane-spanning domains and a long cytoplasmic domain which contains putative protein kinase phosphorylation motifs. NHE-3 exhibits overall 41% amino acid identity with NHE-1. NHE-3 is likely a glycoprotein as it has one potential N-linked glycosylation site, which is conserved in all NHEs identified. Northern blot analysis of poly(A+) RNA isolated from rabbit ileum using NHE-3 cDNA as a probe hybridized to a single 5.4-kilobase transcript. More detailed tissue distribution of message was performed by ribonuclease protection assay. It was found that NHE-3 message is only expressed in intestine and kidney, with the kidney cortex having the most abundant message, followed by intestine and kidney medulla. In intestine, ileum and ascending colon have the same amount of message, with much lesser amounts in jejunum. The message is absent from duodenum and descending colon, which lack the neutral NaCl absorptive process. Thus, NHE-3 might be involved in Na+ absorption in intestinal and renal epithelial cells.
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PMID:Cloning and sequencing of a rabbit cDNA encoding an intestinal and kidney-specific Na+/H+ exchanger isoform (NHE-3). 137 92

1. A ribonuclease isolated from porcine thyroid cytosol using phenol: sodium dodecylsulfate treatment was associated with RNA and identical to latent alkaline ribonuclease. 2. Distribution of activity between aqueous and phenolic phases depended on pH, RNA, and ribonuclease inhibitor. 3. The ribonuclease was totally resistant to urea, guanidinium: HCl, chloroform:isoamyl alcohol, ethanol, heating at 100 degrees C for 10 min or at 80 degrees C plus 100 mM NaCl. It was highly resistant to hydrolysis by proteinase K except in the presence of detergent. 4. The extreme stability and other properties of latent alkaline ribonuclease could be the result of its association with RNA.
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PMID:Porcine thyroid cytosolic, latent alkaline ribonuclease: resistance to protein denaturants. 149 76

A ribonuclease activity in a 100,000 x g supernatant of a Triton lysate of a mitochondrial-kinetoplast fraction from Leishmania tarentolae is activated by incubation with heparin or by predigestion of the lysate with proteinase k or pronase. In vitro-transcribed pre-edited cytochrome b mRNA is cleaved at several sites. With time, complete degradation of the RNA occurs. All cleavages occurred within putative single-stranded regions of the RNA. No cleavage was observed with 9 S rRNA. The presence of a nonspecific nucleotide or nucleoside slows the rate of cleavage. The cleavage activity is inhibited by sodium dodecyl sulfate or phenol/chloroform extraction, is retained by a 10-kDa cutoff filter, and passes through a 30-kDa filter. Micrococcal nuclease inhibits the proteinase-induced activity but not the heparin-induced activity.
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PMID:A ribonuclease activity is activated by heparin or by digestion with proteinase K in mitochondrial extracts of Leishmania tarentolae. 155 86

Thioredoxin (Trx) from Escherichia coli was compared with bovine protein disulfide-isomerase (PDI) for its ability to catalyze native disulfide formation in either reduced or randomly oxidized (scrambled) ribonuclease A (RNase). On a molar basis, a 100-fold higher concentration of Trx than of PDI was required to give the same rate of native disulfide formation measured as recovery of RNase activity. A Pro-34 to His (P34H Trx) mutation in the active site of E. coli Trx (WCGPC), mimicking the two suggested active sites in PDI (WCGHC), increased the catalytic activity in disulfide formation about 10-fold. The mutant P34H Trx displayed a 35-mV higher redox potential (E'0) of the active site disulfide/dithiol relative to wild type Trx, making it more similar to the redox potential observed for PDI. This higher redox potential correlates well with the enhanced activity and suggests a role for the histidine side chain. Enzymatic isomerization of disulfides in scrambled, oxidized RNase requires the presence of a catalytic thiol such as GSH to initiate the thiol-disulfide interchange. Bovine thioredoxin reductase, together with NADPH, could replace GSH. For oxidative folding of reduced RNase in air with Trx, P34H Trx, or PDI, catalytic amounts of sodium selenite (1 microM) resulted in rapid disulfide formation and high yields of ribonuclease activity equivalent to previously known redox buffers of GSH and GSSG. These results demonstrate no obligatory role for glutathione in disulfide formation. A possible mechanism for the unknown thiol oxidative process accompanying folding and protein disulfide formation in vivo is discussed.
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PMID:A Pro to His mutation in active site of thioredoxin increases its disulfide-isomerase activity 10-fold. New refolding systems for reduced or randomly oxidized ribonuclease. 157 42

We have reported previously [Sakakibara, et al. (1991) Chem. Pharm. Bull. 39, 146-149] that a protein purified from a partially purified pharmaceutical preparation of human chorionic gonadotropin (a urinary protein preparation from pregnant women) is a unique nonsecretory ribonuclease (RNase)-like protein on the basis of its amino terminal sequence homology. We purified the protein further from the same materials by gel filtration and reversed-phase column chromatographies with RNase activity as an index. The purified protein was designated RNase UpI-2. The catalytic activity and its sensitivity to inhibition by divalent cations suggest that the protein is related to nonsecretory RNase. The estimated molecular weight of RNase UpI-2 (38 kDa) by sodium dodecyl sulfate-polyacrylamide gel electrophoresis was significantly higher than that of urinary nonsecretory RNases (13 to 19 kDa) reported so far. After trifluoromethanesulfonic acid treatment, the molecular weight of RNase UpI-2 was reduced and approached that of nonsecretory RNase, which indicated that the protein contains a significant amount of carbohydrate (approximately 50%). RNase UpI-2 was immunoreactive with antibodies to a nonsecretory RNase, RNAase 1 [Yasuda et al. (1988) Biochim. Biophys. Acta 965, 185-194]. By immunoblot analysis of the protein freshly prepared from various urine samples, it was shown that a considerable amount of RNase UpI-2 is present in urine of pregnant women, but only a trace of RNase UpI-2, if any, was detected in urine of nonpregnant women and men. These results suggest the possibility that RNase UpI-2 may have been formed via a specific protein modification in pregnant women.
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PMID:Characterization of a unique nonsecretory ribonuclease from urine of pregnant women. 158 93

The nucleosomes of transcriptionally active genes can be separated from those of inactive genes by affinity chromatography on organomercury-agarose (Hg-agarose) columns. The basis for this separation is the difference in accessibility of the sulfhydryl groups of histone H3 and certain non-histone proteins in active and inactive chromatin. A new procedure distinguishing between different modes of binding of transcriptionally active nucleosomes to the Hg-agarose column has been applied to study several factors which might influence the binding reaction. Nucleosomes that bind to the column because of salt-labile associations with SH-reactive non-histone proteins, such as the high-mobility-group proteins, HMG-1 and HMG-2, were released by adding 0.5 M NaCl to the eluting buffer. The remaining nucleosomes, in which reactive histone H3 thiol groups can bind covalently to the organomercury, were then displaced from the column by 10 mM dithiothreitol. Both Hg-agarose-bound fractions contain the transcriptionally active DNA sequences of the cell, but inactive nucleosomes, such as those containing alpha-globin DNA, pass through the column. The histones of both Hg-agarose-bound fractions have significantly higher levels of acetylation than do histones of the unbound fraction, but the content of tri- and tetra-acetylated H3 and H4 is significantly higher in the nucleosomes with reactive H3 thiols. The rate of turnover of histone N-acetyl groups is also far greater in the Hg-agarose-bound nucleosomes than in the unbound nucleosomes. Although the overall levels of histone acetylation can be increased significantly by incubating HeLa cells in the presence of the deacetylase inhibitor, 5 mM sodium butyrate, this treatment has little if any effect on the total number of nucleosomes retained on the Hg-agarose column. However, the ability of Hg-agarose chromatography to detect localized changes in chromatin structure is evidenced by an 11-fold increase in the Hg-agarose binding of nucleosomes containing the DNA of the butyrate-inducible alkaline phosphatase gene, compared to the Hg-agarose-bound nucleosomes of control cells. Although nascent RNA chains are present in the Hg-agarose-bound nucleosomes released by dithiothreitol, binding of the SH-reactive nucleosomes to the Hg-agarose column is not dependent on the presence of proteins associated with nascent RNA chains, since binding does not decrease following removal of the nascent transcripts by ribonuclease treatment.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Factors affecting nucleosome structure in transcriptionally active chromatin. Histone acetylation, nascent RNA and inhibitors of RNA synthesis. 170 16

A procedure for the purification of Neisseria meningitidis lipopolysaccharide (LPS) from outer membrane vesicles (OMV) in spent growth media was developed. Five different LPS strains of group A N. meningitidis were grown in tryptic soy broth with vigorous aeration for 36-48 h, and centrifuged to collect both cells and supernatants. The amount of LPS in the OMV in the supernatants was higher or at least equal to that in the cells. The OMV in each supernatant were concentrated, pelleted by ultracentrifugation, and treated with 2% sodium deoxycholate to dissociate LPS from OMV. The LPS was then separated from capsular polysaccharides, proteins and phospholipids by gel filtration on Sephacryl S-300 column in 1% sodium deoxycholate, and precipitated from the column fractions in 70% ethanol. In addition, LPS was also extracted from cells with hot phenol-water, ultracentrifuged once after treatment with ribonuclease, and purified on Sephacryl S-300. When compared with an improved phenol-water extraction method, the LPS obtained from either OMV or cells by the above methods gave a 40-180% increase in yield. The LPS also had much higher activities in limulus amebocyte lysate assay, rabbit pyrogenic test, and enzyme-linked immunosorbent assay. The LPS purified from cells and from OMV were indistinguishable by sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis.
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PMID:Purification of rough-type lipopolysaccharides of Neisseria meningitidis from cells and outer membrane vesicles in spent media. 177 80

Two neutral ribonucleases have been purified from developing tomato fruit. Their activity is maximal 5 days after anthesis, declines during maturation, and then increases slightly in the mature green through breaker stages. The ribonucleases Tf1 and Tf2 have molecular weights of 59 and 29 K, respectively, based on sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and are glycoproteins. The reduced and denatured Tf1 is composed of two subunits, 30 and 29 K, of which only the 30-K subunit displays ribonuclease activity after renaturation. Reduced and denatured Tf2 is a single 29-K polypeptide that is renaturable to an active ribonuclease. Only the 30-K, active subunit of Tf1 is immunologically cross-reactive with Tf2. Both ribonucleases are cyclyzing endoribonucleases with a strong preference for cleavage at pyrimidine residues, thus generating oligonucleotide products ending with pyrimidine 2',3'-cyclic phosphate. These tomato fruit ribonucleases share a number of properties in common with the S-glycoprotein ribonucleases that are involved in self-incompatibility reactions in some solanaceous plants.
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PMID:Purification and characterization of two ribonucleases from developing tomato fruit. 192 99


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