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 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

Three types of immunoadsorbents were synthetized by antigen coupling to glutaraldehyde-activated polyacrylamide gel, BrCN-activated sepharose 4B and protein insolubilization using glutaraldehyde as a cross-linking agent. Different concentrations of rabbit gamma globulin, bovine serum albumin, soybean trypsin inhibitor and bovine ribonuclease were used as antigens and some properties of such immunoadsorbents were studied. Using 125J labelled antigens it was shown that glutaraldehyde-activated polyacrylamide gel (Bio-Gel P-300) couples 81-94% of the antigen added in a concentration of 0.5-4.0 mg.ml-1 gel and BrCN-activated sepharose 4B bounds 62-88% of the labelled antigen in a concentration of 5.0-20.0 mg.ml-1 gel. These antigen derivatives as well as those obtained by glutaraldehyde protein insolubilization permitted 54-88% of antibodies added with the immune sera to be isolated. There was a significant antigen leakage from sepharose immunoadsorbents after several antisera treatments or after half a year storage but despite of this antigen desorption all types of the immunoadsorbents studied preserved their antibody isolation capacity. Immune sera immunoglobulins nonspecific binding by immunoadsorbents was less on sepharose than Bio-Gel antigen derivatives.
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PMID:[Properties of immunoadsorbents prepared by antigen coupling to glutaraldehydeactivated polyacrylamide gel, BrCN-activated Sepharose and by copolymerization of antigens by glutaraldehyde]. 9 83

This paper demonstrates the existence of regions in eight small globular proteins in which the side chains of sulfur-containing amino acids (cysteine and methionine) alternate in space with side chains of aromatic amino acids (histidine, phenylalanine, tryptophan and tyrosine). The proteins are: rubredoxin, high potential iron protein, cytochrome c, flavodoxin, deoxyhemoglobin, trypsin inhibitor, ribonuclease-S, and lysozyme. The sulfur-pi-bonded 'chains' involve a minimum of five and a maximum of 10 amino acids, and contain the most polarizable atoms within proteins. S-pi-chains give extra stability to the folding of proteins; they may also afford paths for the step-wise movement of electrons.
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PMID:Chains of alternating sulfur and pi-bonded atoms in eight small proteins. 20 19

The effects of 25 to 75 volume-% ethanol on conformation of human serum alpha1-acid glycoprotein, human serum alpha1-antitrypsin, pancreatic deoxyribonuclease I, porcine pepsinogen, the "Kunitz" trypsin inhibitor from soybeans, and oxidized as well as reduced and S-carboxymethylated ribonucleases were tested by the circular dichroism (CD) probe. It was found that 25 volume-% ethanol had a slight effect, whereas 50--75 vol.-% alcohol significantly altered the conformation. The tertiary structure was perturbed and the polypeptide main chain was reorganized into new conformations of higher helix and beta-structure contents than in the native state. Comparison of the various proteins showed that the degree of reorganization depended chiefly on the cross-linking of the main chain by disulfide bridges. While the unfolded ribonucleases were refolded by 25 vol.-% ethanol into ordered conformations, the native ribonuclease and alpha1-antitrypsin was more sensitive to 25 vol.-% ethanol than the conformation of alpha1-acid glycoprotein, pepsinogen, and soybean trypsin inhibitor. Almost complete restoration of the native conformation was achieved by diluting the alcohol-containing solutions with water or by dialysis against water or buffer solutions. However, the renaturation depended on the time of contact with alcohol and on the temperature at which the alcohol-containing solutions were kept.
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PMID:Circular dichroism studies on the effects of ethanol on the conformation of alpha1-acid glycoprotein, alpha1-antitrypsin, deoxyribonuclease, pepsinogen, soybean trypsin inhibitor and unfolded ribonucleases. 30 38

Interactions of several proteins with glutathione-insulin transhydrogenase (GIT) have been investigated by determining their ability to inhibit degradation of 125I-labeled insulin catalyzed by GIT. The inhibition by every insulin analog (des-Asn-des-Ala-pork insulin, desoctapeptide-pork insulin, des-Ala-pork insulin, pork insulin, proinsulin, and guinea pig insulin) was competitive vs. competitive vs. insulin indicating that they function as alternate substrates. The insulin analogs with the least hormonal activity showed the highest potency as inhigitors of insulin degradation. Whereas native ribonuclease and lysozyme showed little or no inhibition, their scrambled forms (i.e. reduced and randomly reoxidized) showed competitive inhibition with a potency greater than that of insulin. These results suggest that the conformation of the substrate or inhibitor is probably the major factor in determining the specificity for (or binding to) the enzyme. Studies withother peptide hormones showed competitive inhibition with vasopressin and oxytocin and noncompetitive inhibition with glycagon. The inhibition with growth hormone could be either competitive or noncompetitive. The inhibition by glucagon and growth hormone (physiologic antagonists of insulin) could serve as a control mechanism to modulate the activity of enzyme. The following showed very little or no inhibition; the native and scrambled form of pepsinogen, trypsin inhibitor of beef pancreas and of lima bean, C-peptide of pork proinsulin, and heptapeptide (B23-B29) of insulin.
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PMID:Interaction of insulin analogs, glucagon, growth hormone, vasopressin, oxytocin, and scrambled forms of ribonuclease and lysozyme with glytathione-insulin transhydrogenase (thiol: protein-disulfide oxidoreductase): dependence upon conformation. 117 Aug 77

We examined the role of physiologic plasma concentrations of cholecystokinin (CCK) in the regulation of rat pancreatic gene expression. Postprandial plasma CCK concentrations, as determined by bioassay, were achieved by intraduodenal perfusion with soybean trypsin inhibitor (SBTI) or intravenous infusion of CCK-8. SBTI administration for 48h resulted in nonparallel regulation of digestive enzyme gene expression, as assessed by slot-blot analysis using cloned cDNA probes for trypsin, chymotrypsin, amylase and ribonuclease. As an indicator for pancretic growth stimulation, ornithine decarboxylase (ODC) gene expression was stimulated appr. 2-fold over the SBTI infusion period. Identical effects were seen with i.v. infusion of CCK-8. The CCK receptor antagonist L-364, 718 blocked the effects on pancreatic gene expression of both CCK infusion and SBTI administration. These data therefore indicate that postprandial plasma CCK concentrations regulate pancreatic digestive enzyme and ODC gene expression at a pretranslational level.
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PMID:Cholecystokinin as a regulator of rat pancreatic gene expression. 171 83

A new and simple method to measure 3JHNH alpha coupling constants of proteins by adding and subtracting traces from corresponding two-dimensional nuclear Overhauser enhanced spectroscopy and two-dimensional correlated spectroscopy cross peaks after scaling is proposed. The optimal scaling for the addition and the subtraction of the two traces is obtained by minimizing an error function. The method was proven to give accurate and precise measurements of coupling constants when tested with a series of simulated spectra. The accuracy of the method was better than 0.1 Hz for all test cases including the limiting case of J = 2.0 Hz and line-width = 11.0 Hz. The accuracy of the method was better than 0.1 Hz for all test cases including The 3JHNH alpha coupling constants were measured in two-dimensional nuclear magnetic resonance spectra of the two proteins barley serine proteinase inhibitor (CI-2) and the bacterial ribonuclease (barnase) of Bacillus amyloliquefaciens. The experimentally measured coupling constants were used to calculate the constants in a Karplus equation to be: 3JHNH alpha = 6.7 cos2(phi-60) -1.3 cos(phi-60) +1.5. These constants are in good accordance with those obtained for basic pancreatic trypsin inhibitor (BPTI). In addition, special emphasis is given to the measurements of positive phi-angles, and to the contribution of molecular dynamics on the apparent coupling constants.
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PMID:Accurate measurements of coupling constants from two-dimensional nuclear magnetic resonance spectra of proteins and determination of phi-angles. 200 22

The attempt is made to find new correlations between local structural characteristics of proteins and the hydrogen exchange rates of their individual main-chain amides, and to relate such correlations to possible mechanisms of hydrogen exchange. It is found that in bovine pancreatic trypsin inhibitor (BPTI) the surface area buried by a particular residue and its neighbors correlates with the exchange rate of the main-chain amide of that residue. As the area buried by a particular fragment can be associated with the stabilization of the protein structure by this fragment, the correlation suggests a role for the energetics of the local unfolding in the mechanism of hydrogen exchange. Calculations based on the assumption that the exchange mechanism involves local unfolding lead to quantitative agreement between the calculated and experimentally measured exchange rates for 80% of the amides of BPTI that are buried or hydrogen bonded to the main-chain or to internal water molecules. The same degree of correlation is found between the calculated exchange rates and partial exchange data for ribonuclease S, hen lysozyme and cytochrome c. A similarly strong correlation is found between calculated exchange rates and the exchange rates of ribonuclease A determined by neutron diffraction in the crystal. The criteria of correlation are, however, less stringent in this case because of the experimental errors, which are larger than for solution data. It is suggested that the observed correlation be used for predictions of hydrogen exchange rates in proteins.
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PMID:Correlation between calculated local stability and hydrogen exchange rates in proteins. 244 80

Regulation of pancreatic gene expression by cholecystokinin (CCK) was examined in the rat using cloned cDNA probes to quantify changes in specific mRNAs (amylase, trypsinogen I, chymotrypsinogen B, and ribonuclease). Rats were administered intraduodenally an elemental liquid diet. Plasma CCK levels were raised to levels comparable to physiological postprandial levels either by intraduodenal perfusion with soybean trypsin inhibitor (SBTI) (6.9 +/- 1.0 pM, n = 8) or by continuous intravenous infusion with cholecystokinin octapeptide (CCK-8, 6.0 +/- 0.9 pM, n = 6). SBTI infusion resulted in fivefold increases in trypsinogen I and chymotrypsinogen B mRNA levels after 48 h. In contrast SBTI infusion had no effect on amylase mRNA levels and led to a decrease in ribonuclease mRNA levels to approximately 50% of control after 48 h. Intravenous infusion with CCK-8 for 24 h resulted in plasma levels of CCK comparable to those obtained with SBTI and had similar effects on digestive enzyme mRNA levels. These data suggested that SBTI acted via its ability to raise plasma CCK levels. To further test the specificity of these effects, animals were infused intraduodenally with the specific CCK receptor antagonist L364,718. Although the antagonist itself had no effect on digestive enzyme mRNA levels, antagonist treatment totally abolished the effects of both CCK infusion and SBTI treatment. These data therefore indicate that CCK regulates digestive enzyme gene expression at plasma concentrations comparable to physiological postprandial levels. Furthermore, the ability of SBTI infusion to increase plasma CCK accounts for its effects on pancreatic digestive enzyme mRNA levels.
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PMID:Pancreatic digestive enzyme gene expression: effects of CCK and soybean trypsin inhibitor. 246 94

We have developed a new method for modelling protein dynamics using normal-mode analysis in internal co-ordinates. This method, normal-mode dynamics, is particularly well suited for modelling collective motion, makes possible direct visualization of biologically interesting modes, and is complementary to the more time-consuming simulation of molecular dynamics trajectories. The essential assumption and limitation of normal-mode analysis is that the molecular potential energy varies quadratically. Our study starts with energy minimization of the X-ray co-ordinates with respect to the single-bond torsion angles. The main technical task is the calculation of second derivative matrices of kinetic and potential energy with respect to the torsion angle co-ordinates. These enter into a generalized eigenvalue problem, and the final eigenvalues and eigenvectors provide a complete description of the motion in the basic 0.1 to 10 picosecond range. Thermodynamic averages of amplitudes, fluctuations and correlations can be calculated efficiently using analytical formulae. The general method presented here is applied to four proteins, trypsin inhibitor, crambin, ribonuclease and lysozyme. When the resulting atomic motion is visualized by computer graphics, it is clear that the motion of each protein is collective with all atoms participating in each mode. The slow modes, with frequencies of below 10 cm-1 (a period of 3 ps), are the most interesting in that the motion in these modes is segmental. The root-mean-square atomic fluctuations, which are dominated by a few slow modes, agree well with experimental temperature factors (B values). The normal-mode dynamics of these four proteins have many features in common, although in the larger molecules, lysozyme and ribonuclease, there is low frequency domain motion about the active site.
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PMID:Protein normal-mode dynamics: trypsin inhibitor, crambin, ribonuclease and lysozyme. 258 Jan 1


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