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)

Specific beta-adrenergic receptors present in membrane preparations of frog erythrocytes were identified by binding of (-)-[3H]dihydroalprenolol, a potent competitive beta-adrenergic antagonist. The (-)-[3H]dihydroalprenolol binding sites could be solubilized by treatment of a purified erythrocyte membrane fraction with the plant glycoside digitonin but not by treatment with a wide variety of other detergents. The binding sites appeared to be soluble by several independent experimental criteria including (a) failure to sediment of 105,000 X g for 2 hours; (b) passage through 0.22-mu Millipore filters; (c) chromatography on Sepharose 6B gels; and (d) electron microscopy. The soluble receptor sites retained all of the essential characteristics of the membrane-bound sites, namely rapid and reversible binding of beta-adrenergic agonists and antagonists; strict stereospecificity toward both beta-adrenergic agonists and antagonists; appropriate structure-activity relationships; saturability of the sites at low concentrations of ligand; no affinity for alpha-adrenergic drugs, nonphysiologically active catechol compounds, and catecholamine metabolites. Based on gel chromatography in the presence of detergent, the molecular weight of the soluble receptor is estimated to be no greater than 130,000 to 150,000. Equilibrium binding studies indicated a KD for the soluble receptor of 2 nM. Hill coefficients (nH) of 0.77 and curved Scatchard plots suggested the presence of negatively cooperative interactions among the solubilized receptors in agreement with previous findings with the membrane-bound sites. Kinetic studies indicated an association rate constant K1 = 3.8 X 10(6) M-1 min-1 and a reverse rate constant k2 = 2.3 X 10(-3) min-1 at 4 degrees. The kinetically derived KD (k2/k1) of 0.6 nM is in reasonable agreement with that determined by equilibrium studies. The soluble receptors were labile at temperature greater than 4 degrees but could be stabilized with high concentrations of EDTA. Guanidine hydrochloride and urea produced concentration-dependent losses of binding activity which were partially reversible upon dialysis. Trypsin and phospholipase A both degraded the soluble receptors but a variety of other proteases and phospholipases as well as DNase and RNase were without effect. Experiments with group-specific reagents indicated that free lysine, tryptophan, serine, and sulfhydryl groups may be important for receptor binding. These studies suggest that the receptor is probably a protein which requires lipids for functional integrity. Data obtained with the solubilized binding sites are consistent with the contention that these sites represent the physiologically relevant beta-adrenergic receptors which have been extracted from the membranes with full retention of their properties.
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PMID:Solubilization and characterization of the beta-adrenergic receptor binding sites of frog erythrocytes. 0 47

Two RNases in bound forms associated with the microsomal membrane and with the ribosomes or unknown particles in pea root tissue were solubilized by subjecting the membrane to sonic oscillation in the presence of EDTA and KC1 and by treating the particles with EDTA, respectively. The RNases were than purified by DEAE-cellulose and Sephadex G-75 column chromatographies. The elution profiles of RNases from the columns were very similar. No significant differences were observed in their electrophoretic mobilities in polyacrylamide gels, in molecular weight, in activation by inorganic ions, urea or phospholipid micelles or in the dependence of their activities upon pH. The purified RNASES were not different from the bound enzymes as regards activation by inorganic ions and urea and the dependence of the activity upon pH. Triton X-100 stimulated the activity only if RNase was in a bound form associated with the microsomal membrane. We propose that the two RNases may be the same molecular species and differ only in the form of association with intracellular structures.
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PMID:Purification and properties of two ribonucleases in different intracellular compartments in pea root tissue. 0 8

The presence of a nuclear DNA polymerase in mouse sperm from adult testes has been confirmed and the properties of this enzyme further investigated. This activity was shown to be greatly enhanced by treating the spermatozoa with methanol or ethanol before incubation in the reaction medium or by their addition in small amounts to this medium. It was protected against degradation by nuclear proteases by adding soybean trypsin inhibitor and was stimulated by ATP. It was found to be Mg2+ dependent (optimum concentration: 7.5 mM), DNA dependent, and all four deoxynucleoside triphosphates were needed for optimal reaction. The radioactive acid-precipitable product of polymerization was not eliminated by organic solvents, nor by pronase, ribonuclease or by nuclease S1; however, it was converted to a large extent to acid-soluble products by pancreatic deoxyribonuclease. Since it was only partially solubilized by Triton X-100, it therefore did not appear to be preferentially associated with the nuclear membranes. The activity recovered after incubation depended also on the pH (optimum at pH 8.3) and did not work well in a medium for DNA polymerase alpha. The temperature for maximum incorporation of nucleotides was found to be 32 degrees C and, under our conditions, the reaction was linear for 30 min. The DNA polymerase activity was inhibited by low and high concentrations of KCl. It was not lowered by N-ethylmaleimide or p-hydroxymercuribenzoate; urea slightly stimulated the reaction and this stimulation was reversed by subsequent treatment with N-ethylmaleimide. Actinomycin D (40 mug/ml), ethidium bromide (25--50 muM), netropsin (5--50 mug/ml), and spermidine (0.5--2.5 mM) lowered the polymerization of DNA precursors. The nuclear enzyme could shift from the endogenous template to activated exogenous calf thymus DNA, the resulting nuclear radioactivity being reduced. The endogenous DNP template ability was not increased by deoxyribonuclease activation according to the method of Aposhian and Kornberg (J. Biol. Chem. (1962) 237, 519--525) suggesting that the amount of DNA polymerase associated with chromatin was probably limiting the reaction. The DNA polymerase activity detected in mouse sperm nuclei has numerous properties of low molecular weight DNA polymerases (DNA polymerase beta) reported in several eukaryotic organisms.
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PMID:Further characterization of a DNA polymerase activity in mouse sperm nuclei. 1 3

Five ribonuclease activities, separable by polyacrylamide gel electrophoresis, have been detected in erythroid bone marrow cells from anaemic rabbits. Their intracellular distribution has been investigated and compared with that of the ribonucleases in reticulocytes. Both the acid and alkaline ribonuclease activities of reticulocytes are much lower (30--50 fold) than those of bone marrow erythroid cells. The most marked decrease in enzyme activity occurs in the fractions containing ribosomes and mitochondria plus lysosomes. In these subcellular organelles there was also a qualitative change in the ribonuclease electrophoretic pattern, whereas the cytosol enzymes of marrow erythroid cells and reticulocytes remained largely unchanged. Several ribonucleases released from reticulocyte membranes with urea were similar to those present in the lysosomal plus mitochondrial fraction, as shown by detection of enzyme activity after polyacrylamide gel electrophoresis. The decline in ribonuclease activity was found to begin in the orthochromatic cells, which have a highly condensed nucleus and are no longer active in DNA and RNA synthesis, and to coincide with a decrease in acid phosphatase activity and loss of lysosomes.
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PMID:Intracellular distribution of ribonuclease activity during erythroid cell development. 1 51

Radioactive selenite reacts with purified human and goat immunoglobulins at acidic and neutral pH. The antigenic properties of the immunoglobulins are retained during the selenium labelling as shown by immunoelectrophoresis and autoradiography. Pepsin digests of 75Se-labelled IgG possess 75Se both in the (Fab')2 fraction and in the low molecular weight peptides derived from the Fc domains. Alpha-1-acid glycoprotein, ribonuclease, and lysozyme are also labelled by this procedure. Enhancement of 75Se incorporation by urea, guanidinium chloride, mercaptoethanol, sodium sulfite and carrier selenite is interpreted as an effect of destabilization of IgG disulfide bonds. Up to 1.4 g atoms Se per mol IgG have been incorporated. We assume that selenite is cleaving disulfides by a process akin to sulfitolysis. The lability of the isolated 75Se-labelled IgG to high concentrations of mercaptans and sulfite is consistent with this idea. These 75Se-labelled proteins may be useful in structure studies and radioimmunoassay.
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PMID:Reaction of selenium with immunoglobulin molecules. 1 84

In an investigation into the disturbances of body function associated with burn injury we have measured the activity of alkaline ribonuclease (EC 3.1.4.22) and the level of urate in the serum and urine of patients sustaining burn injury. Ribonuclease activity was elevated in all patients. The degree of elevation can be related to the percentage of the body surface area burned and to a predictive index of burn mortality. Increased serum ribonuclease activity was accompanied by increased urine ribonuclease output. The relationship between serum urea and ribonuclease activity has been investigated. A significant correlation between these two parameters was observed during the first week post burn. We suggest that this correlation shows as a result of increased protein catabolism and renal dysfunction. After the first week a significant correlation between serum urea and ribonuclease activity was not observed. It is possible that, at this stage, increased ribonuclease activity is perhaps a result of tissue repair. Serum urate was found to be decreased in all patients after burn injury. Serum urate decrease expressed as a percentage of initial value, correlated very strongly with the predictive index of burn mortality. In severely burned patients the decrease in serum urate was accompanied by increased urine urate output and may indicate a change in renal handling of urate after burn injury.
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PMID:Observations on serum and urine alkaline ribonuclease activity and urate after burn injury in man. 2 22

By sequential acid treatment, gel filtration and KM-cellulose sorption a 18--20-fold purified preparation of ribonuclease with a yield of 50--60% was obtained from the culture liquid filtrate of Actinomyces rimosus 994. The preparation had a high specific activity of 450,000--600,000 units/mg protein, contained 85--98% protein, insignificant amounts of carbohydrates and hydroxytetracycline, and no quantities of DNase, phosphomonoesterases, phosphodiesterase or proteases. In RNA degradation (preparation of the total yeast RNA of the Sigma Co.) optimal results were obtained at 50 degrees C and pH 7.0--7.2 in phosphate buffer and 7.6--8.0 IN Tris-HCl buffer. The preparation was stable at high temperatures (80--100 degrees) in the wide pH range and during storage in the lyophilized form and in buffer solutions. RNase effect was inhibited by zinc, copper, iron and cobalt cations and activated by beta-mercaptoethanol, citrate and EDTA. Protamine sulphate and urea in low concentrations (0.01% and 1--4 M, respectively) accelerated and in high concentrations (1% and 8 M, respectively) terminated the enzyme reaction. With respect to many properties RNase from Act. rimosus 994 was similar to extracellular RNases, produced by other actinomycetes and fungi.
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PMID:[Preparation of extracellular ribonuclease form Actinomyces rimosus 994]. 3 16

Temperature-jump relaxation studies in deoxy-ribonuclease I were carried out at 10 degrees C and [I] = 0.1 M. The single observed relaxation time, which varied from 10(-4) to 10(-5) s, was characterized as a function of enzyme concentration, pH, and indicator concentration. The concentration and pH dependences of the relaxation time are in quantitative agreement with a mechanism involving an isomerization of the enzyme coupled to a rapid proton ionization process. The best fit forward and reverse isomerization rate constants are 6.5 X 10(3) and 7.2 X 10(4) s-1, respectively; the apparent pK is 5.7. The addition of urea brought about reductions in both the amplitude of the relaxation effect and the enzyme activity.
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PMID:Relaxation studies of enzymes: rapid isomerization in deoxyribonuclease I. 3 22

Western equine encephalitis virus was disrupted with Triton X-100 and subjected to isoelectric focusing in a sucrose or urea gradient. The two envelope proteins, E1 and E2 were not well separated in a sucrose gradient, while the E1 and E2 proteins were distinguished as two major peaks which focused in a urea gradient at about pH 7.5 and 10, respectively. Isolated E1 protein refocused at pH 6.5 in a sucrose gradient isoelectric focusing column. When Western equine encephalitis virus was treated with Triton X-100 in 0.01 M phosphate buffer (pH6), hemagglutinating E1 protein was solubilized, which isoelectrofocused at pH 6.5. Purified nucleocapsids focused at pH 4 in a sucrose gradient on an isoelectric focusing column. After ribonuclease treatment of the purified nucleocapsid more than 95 per cent of the viral RNA was acid-soluble, and hte nucleocapsid protein isoelectrofocused at about pH 4.
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PMID:Isolation of the structural proteins of western equine encephalitis virus by isoelectric focusing. 4 5

Cultures of foetal human pituitary cells excrete and synthetize different molecular forms of proteins with HGH immunological activity. These cells incorporate tritiated-leucine in these proteins. Gel chromatography on sephadex using different length of column allow us to separate: One form excluded in front of the dead volume and which has a high molecular weight. This form is not dissociated by treatment with urea 8 M, guanidine 6 M and dithiothreitol. Nor this form is modified by treatment by ribonuclease. One form excluded within the dead volume and which is probably a dimere. This form is no more modified by the different treatments. One form which is excluded like a monomere--it is the more important form--. This form is dissociated in fragments of lower molecular weight by urea 8 M. This dissociation is partially reversible by dialysis.
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PMID:[Molecular forms of human growth hormone (HGH) secreted by cultured fetal pituitary cells]. 14 Jul 46


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