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 cytoplasmic, microsomal bound RNA-dependent RNA polymerase has been purified 2500-fold from rabbit reticulocyte lysates. The synthesis of RNA with the purified enzyme is absolutely dependent on the addition of an RNA template. The best template is hemoglobin messenger RNA, while bacteriophage RNA and poly(A,G) are less active, and DNA is completely inactive as a template. With poly(A,G) as a template, only UTP and CTP are incorporated into polynucleotide chains, indicating that the RNA polymerase is an RNA replicase and not a terminal transferase. With messenger RNA as a template, all four ribonucleoside triphosphates are required for maximal activity. The RNA-dependent RNA polymerase reaction is extremely sensitive to low concentrations of heme, rifamycin AF/013, and ribonuclease and resistant to actinomycin D and DNase. The discovery of RNA-directed RNA synthesis in reticulocytes offers an additional site for control of gene expression in mammalian cells and provides a possible mechanism for amplification of the expression of specific genes.
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PMID:Reticulocyte RNA-dependent RNA polymerase. 451 33

Spectrin in isolated erythrocyte membranes is known to undergo tetramer to dimer transformation upon hypotonic incubation at 37 degrees C. In the present study, we detect no such transformation in intact erythrocytes in which hypotonicity is achieved by valinomycin treatment followed by hypotonic swelling. The inhibition of spectrin tetramer to dimer transformation is attributable to intracellular hemoglobin, since the addition of hemoglobin to isolated membranes or spectrin extracts blocks a similar spectrin transformation. However, the inhibitory effect is not limited to hemoglobin; other proteins including heme-containing proteins and basic proteins such as cytochrome c, ribonuclease, and albumin are also effective. The magnitude of their effect is proportional to the increased pI value of these proteins. We conclude that the stabilizing effect of these proteins on spectrin tetramers under hypotonic conditions is partly due to their non-ideality, which excludes water from spectrin and thus increases the effective concentration of spectrin, and to their electrostatic interactions with spectrin. In addition, promotion of spectrin self-association by hemoglobin under hypotonic conditions increases the stability of membrane skeletons against mechanical shearing. More importantly, the hemoglobin effect on spectrin self-association is demonstrable at physiological hemoglobin concentration, pH, and osmolarity, suggesting that in intact red cells the spectrin dimer-dimer association, as well as the membrane skeletal structure, is strengthened by intracellular hemoglobin.
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PMID:Hemoglobin enhances the self-association of spectrin heterodimers in human erythrocytes. 608 50

Models describing the interaction of a small molecule with a protein are typically couched in terms of the stoichiometry, cooperativity, and binding free-energy change. These parameters are readily available from equilibrium dialysis experiments (or appropriate variations). With the recent advent of extremely sensitive calorimeters, it is possible to obtain thermal data for the binding reaction and, thus, the entire set of thermodynamic parameters, delta G', delta H', delta S', delta C', become readily available. This review is limited to the binding of nucleotides and nucleotide analogs to proteins for which complete thermal data are available. While the majority of such systems have been characterized by calorimetry, we have not excluded, per se, van't Hoff enthalpy determinations. The systems we have considered include, but are not limited to, thymidylate synthetase, phosphorylase, several dehydrogenases, aldolase, glutamine synthetase, hemoglobin, asparate transcarbamylase, and ribonuclease. A variety of forces contribute to the total free-energy change upon ligand binding. These forces include ionic, van der Waals, hydrogen bond, and hydrophobic. In several cases, properly designed experiments have allowed a partial resolution of the individual contributions of these various forces. Variation of easily accessible conditions such as temperature, pH, ionic strength, or solvent third component produce changes in the set of thermodynamic parameters which lead to the resolution of the forces. The generality of heat effects makes this method very useful for studying the involvement of protons in binding reactions. The variation in the magnitude and direction (release or uptake) of the proton flux is readily studied by determining the apparent heat of reaction at constant pH, ionic strength, and temperature in two or more buffers of differing heat of ionization. This application has been exploited in several cases and is examined in great detail. An overview of the results in these systems to date suggests that several trends observed in the thermodynamic parameters need to be confirmed by further experimentation and, if they hold, an appropriate theoretical basis must be developed to aid in their interpretation.
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PMID:The thermodynamics of nucleotide binding to proteins. 610 94

The effect of various treatments on the activity of anti-treponemal lymphotoxin (ATL) produced by lymphocytes of syphilitic rabbits was studied. Treponema pallidum-killing activity of ATL was slightly reduced after heating at 56 degrees C and completely abolished at 100 degrees C. The significant reduction of the activity was also obtained after exposure of ATL to acidic conditions (pH 1-5) at room temperature, or by treatment with papain and neuraminidase. Activity of ATL was completely resistant to deoxyribonuclease, ribonuclease and trypsin treatment. ATL was eluted from the Sephadex G-100 column together with hemoglobin, that suggested the apparent molecular weight of ATL of about 65,000. The active fraction from the Sephadex G-100 column was further fractionated on DEAE-Sephadex A-50. The activity of ATL was widely spread in the column eluate, indicating the charge heterogeneity. All these data indicate that ATL is a relatively low molecular weight protein. The sensitivity to neuraminidase and heterogeneity of charge suggest that it is a glycosylated protein.
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PMID:Characterization of anti-treponemal lymphotoxin from lymphocytes of syphilitic rabbits. 638 57

Four zymogens of acidic proteases A, B, C, and D were isolated from the gastric mucosa of harp seals by ion-exchange chromatography on a diethylaminoethyl-Sephadex A-50 column. The major zymogens were A and C, and the ratio of zymogen A to zymogen C was greater in extracts from 1-week-old animals than in extracts from adult animals. Zymogens A and C were further purified by affinity chromatography using carbobenzoxy-D-phenylalaninetriethylene tetramine Sepharose and gel filtration on a Sephadex G-100 column. Certain physical and catalytic properties of proteases A and C were compared with those of calf chymosin (EC 3.4.23.4) and porcine pepsin (EC 3.4.23.1). Zymogen C and the corresponding enzyme were homogeneous on analytical polyacrylamide gel electrophoresis. Zymogen A was homogeneous as judged by sodium dodecyl sulphate (SDS)-polyacrylamide gel electrophoresis and high performance liquid chromatography, but was heterogeneous by polyacrylamide gel electrophoresis at pH 8.3. Zymogens A and C had molecular weights of 33 800 and 44 000, respectively, as estimated by SDS-polyacrylamide gel electrophoresis. Protease A had an isoelectric point of 4.90. Protease A was similar to calf chymosin with respect to several criteria. It had a higher ratio of milk-clotting to proteolytic activity than those of seal protease C and porcine pepsin and had a pH optimum of 2.2-3.5 for hemoglobin hydrolysis. It did not inactivate ribonuclease, had very low activity on N-acetyl-L-phenylalanyl-3,5-diiodo-L-tyrosine and lost activity in 6 M urea. These results indicate protease A is chymosinlike.
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PMID:Purification and characterization of a chymosinlike protease from the gastric mucosa of harp seal (Pagophilus groenlandicus). 643 45

A method for electrophoretic concentration of differently charged proteins is described. A nonlinear pH gradient is generated by imposing a potential gradient on an electrolyte system composed of (+)H3PO4-valine (pI 6.0)-Servalyte (pH 9-11)-triethylamine(-). Proteins contained in the valine solution accumulate at the interphase formed between the valine solution and the Servalyte solution. This interphase acts as a barrier or liquid membrane to all proteins having isoelectric points in the range 6-9. For proteins having isoelectric points in the range 5-7 valine is replaced by histidine (pI 7.64) and the Servalyte by Pharmalyte, pH 2.5-5.0. Ribonuclease, hexokinase, bovine serum albumin, and hemoglobin were concentrated and recovered from the top of the column using a peristaltic pump. The duration of concentration process was 1-4 h, the length of the run depending on the experiment scale (20 or 100 ml protein solution), the amount of protein, and the isoelectric point of the protein. Proteins were concentrated 9- to 48-fold, depending on the initial volume and concentration of the protein. The recoveries ranged from 79.7 +/- 1.1 for hemoglobin to 93.17 +/- 2.84 for ribonuclease.
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PMID:Electrophoretic concentration of proteins in a nonlinear pH gradient. 673 3

The antioxidant activity of skim milk was evaluated in a linoleate emulsion system with hemoglobin as a pro-oxidant. Sonication greatly increased the antioxidant activity of skim milk. The antioxidant activity of the casein fraction of milk was increased most by sonication, and this increase was nearly as great as that for skim milk, suggesting that casein was almost totally responsible for the antioxidant effect of sonication. Total sulfhydryl groups of skim milk decreased upon prolonged sonication, probably the result of the heat evolved in the process. Reactive sulfhydryl content was unchanged by sonication. Sonication had no effect on antioxidant activity of beta-lactoglobulin, reduced urease, or reduced ribonuclease, proteins with free sulfhydryl groups. Apparently sulfhydryl groups were not involved in the increased antioxidant activity of sonicated skim milk. Homogenization at 281.5 kg/cm2 did not increase the antioxidant effect of skim milk. Sonication probably disrupted casein micelles, increasing the effective concentration of casein, which could account for the increased antioxidant activity in the system.
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PMID:Antioxidant activity of skim milk: effect of sonication. 689 12

Previous studies have shown that a neutral metallo-endopeptidase purified from rat kidney degrades the B chain of insulin, glucagon, ACTH and, at a markedly slower rate, the A chain of insulin. In contrast the enzyme does not attack native insulin, oxytocin, vasopressin, ribonuclease, albumin or denatured hemoglobin. The current studies demonstrate that the neutral peptidase also degrades the isolated C-peptide of proinsulin and cleaves certain peptide bonds in and near the C-peptide moiety of native proinsulin. Time courses of the formation of fluorescamine-reactive material during digestion of proinsulin and isolated C-peptide with the peptidase were identical. However, structural analysis of the peptidase-digested proinsulin showed that the enzyme does not convert proinsulin to insulin but that the peptidase cleaves one bond, Tyr26-Thr27, in the B chain moiety and five bonds in the C-peptide moiety, producing four split proinsulins. One of the split proinsulins is des-octacosa-peptide (27-54) porcine proinsulin or des-tetracosapeptide (27-50) bovine proinsulin. Each is a derivative of the insulin molecule having an extension of nine residues (ten residues in the case of the derivative from bovine proinsulin) at the N-terminus of A chain and lacking four residues at the C-terminus of B chain. This two chain derivative retains full immunoreactivity with insulin antibodies and exhibits 2.4-times more biological activity (promotion of glycogenesis in primary cultured hepatocytes) than proinsulin and about two-thirds the activity of insulin.
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PMID:Degradation of proinsulin and isolated C-peptide by rat kidney neutral metallo-endopeptidase. 702 23

Aldose reductase gene expression is increased in insulin-dependent diabetes mellitus (IDDM) with nephropathy. Epidemiology studies in patients with IDDM and noninsulin-dependent diabetes mellitus (NIDDM) are consistent with the hypothesis that a genetic factor(s) influences the risk for kidney disease of diabetes mellitus (KDDM). Aldose reductase (AR), the rate-limiting enzyme in the polyol pathway, is a potential candidate gene product. The present study explored the hypothesis that AR gene expression is increased in peripheral blood mononuclear cells obtained from patients with KDDM. We studied four groups of volunteers: group I, normal subjects; group II, IDDM without nephropathy; group III, IDDM with kidney disease; and group IV, nondiabetics with kidney disease. AR messenger ribonucleic acid was measured by a ribonuclease protection assay. The results are expressed as the mean and 95% confidence interval (CI) of the AR/beta-actin messenger ribonucleic acid molar ratios (AR/beta-actin R). Among diabetics, the AR/beta-actin R was higher in group III (0.088; CI, 0.068-0.108) than in group I (0.045; CI, 0.033-0.057; P < 0.01). There were no significant differences in age, hemoglobin A1c, or duration of diabetes between groups II and III (P = NS). The AR/beta-actin R in group III was also higher than that in group II (0.045; CI, 0.030-0.060; P < 0.01) or group IV (0.019; CI, 0.011-0.027; P < 0.001). In contrast, among nondiabetics, AR/beta-actin R values were 2-fold lower in group IV than in group I (P < 0.01). The results of this study are consistent with the hypothesis that the degree of AR gene expression modulates the risk of KDDM.
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PMID:Aldose reductase gene expression is increased in diabetic nephropathy. 921 10

For eleven films of various water-soluble alpha-, beta-, alpha-/beta-, and alpha-+beta-proteins, the amide-proton exchange, initiated by exposure of the protein film to 2H2O, has been monitored using infrared spectroscopy. The approach to obtain the kinetics of exchange for four different classes of amide protons, correlating to the different secondary structure types, has been described in detail in the preceding paper. In this work the more general applicability of the approach is illustrated by testing it for different types of proteins. The results obtained are shown not only to be comparable to reported time-resolved nuclear magnetic resonance data (as in the case of myoglobin, phospholipase A2, lysozyme, and cytochrome c), or to the more qualitative data obtained by neutron diffraction (trypsin, ribonuclease S, papain, and subtilisin BPN'), but the infrared approach us also provides with quantitative detailed insight on the distribution of exchange rate constants at the submolecular level of proteins, too complex to be studied by other techniques, as for tetrameric hemoglobin, and of proteins in which exchange is too fast to be detected by these other techniques, as is shown in this work for alpha-casein and apocytochrome c.
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PMID:Amide-proton exchange of water-soluble proteins of different structural classes studied at the submolecular level by infrared spectroscopy. 935 29


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