Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.1.27.1 (RNase)
 16,360 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Young rats were force-fed for 3 days a purified diet devoid of threonine and a number of aspects relating to RNA metabolism in the livers were studied. The findings in the livers of rats force-fed the threonine-devoid diet in comparison with those force-fed the complete diet were as follows: a) poly(A)-mRNA was increased in nuclei and in polyribosomes; b) DNA-dependent RNA polymerases I and II activities were increased; c) in vitro release of 14C-orotic acid labeled RNA from nuclei revealed that transport was unchanged and nucleoside triphosphatase activity of nuclear envelopes was unchanged; d) polyribosomes (total, free and membrane-bound) shifted toward heavier aggregation and in vitro 14C-leucine incorporation into protein was increased; e) RNase activities (at pH 5.4, 7.6, 9.5) were essentially unaltered; and f) in vivo 14C-choline incorporation into microsomal membranes was increased. By administering selected inhibitors of RNA and protein synthesis, such as actinomycin D, alpha-amanitin or cycloheximide, prior to killing the rats force-fed the threonine-devoid or complete diet for 3 days, it was demonstrated that the stimulatory effect on hepatic polyribosomes and protein synthesis in the experimental group was dependent upon new synthesis of poly(A)mRNA and of protein.
 ...
PMID:Studies dealing with hepatic RNA metabolism in rats force-fed a threonine-devoid diet. 616 Feb 24

The substrate specificity of pancreatic ribonuclease A is discussed in light of observations based on accurate X-ray structure analysis of several enzyme-nucleotide complexes. A hypothesis for protein-nucleic acid recognition is presented which proposes that: (a) pyrimidine bases in RNA are recognised by ribonuclease due to the charge complementarity of two groups (the amide nitrogen and the side chain oxygen (OG) of threonine 45) of the protein and relevant atoms in the heterocyclic base (O2 and N3 in pyrimidine nucleotides); (b) interaction of the protein with the ribose moiety of the nucleotides is non-specific; and (c) conformational flexibility in the region of the scissile P-O bond is provided by different locations of the phosphoryl oxygens, rather than by an overall translation of the phosphate moiety.
 ...
PMID:Enzyme specificity: base recognition and hydrolysis of RNA by ribonuclease A. 619 18

This paper describes the structure of bovine pancreatic ribonuclease A, refined by a restrained parameter least squares procedure at 2.0 A resolution, and rebuilt using computer graphics. The final agreement factor (formula see text) is 0.159. The positions of the 951 main chain atoms have been determined with an estimated accuracy of 0.17 A. In addition, the model includes a phosphate group in the active site and 176 waters, many of them with partial occupancy. The bond lengths in the refined structure of RNase A differ from the ideal values by an overall root mean square deviation of 0.022 A; the corresponding value for angle distances is 0.06 A. The root mean square deviation of planar atoms from ideality is 0.017 A, and root mean square deviation of the peptide torsion angles from 180 degrees is 3.4 degrees. The model is in good agreement with the final difference Fourier maps. Two active site histidines, His 12 and His 119, form hydrogen bonds to the phosphate ion. His 119 is also hydrogen bonded to the carboxyl of ASp 121 and His 12 to the carbonyl of Thr 45. The structure of the RNase A is very similar to that of RNase S, particularly in the active site region. The root mean square discrepancy of all atoms from residues 1 to 16 and 24 to 123 is 1.06 A and the root mean square discrepancy for the active site region is 0.6 A.
 ...
PMID:The refined crystal structure of ribonuclease A at 2.0 A resolution. 627 80

The results of X-ray analyses of three ribonuclease-A-nucleotide complexes, at 2.3 A, are reported. A modified purine mononucleotide, 8-oxo-guanosine 2'-phosphate in a syn conformation, binds at the pyrimidine-binding site of the catalytic cleft. Solvent molecules are expelled from the active site due to inhibitor binding. The positions of the side-chains of the active-site residues Gln-11, His-12 and Thr-45 are well defined and do not alter on inhibitor binding. The mobility of Lys-41 is greatly reduced in the protein-nucleotide complexes and the terminal amino group interacts directly with the 2'-phosphate group of the nucleotides. In the complex of the enzyme with a modified pyrimidine, cytidine-N(3)-oxide 2'-phosphate, His-119 is stabilised in the minor site of the native protein [Borkakoti, N., Moss, D.S. and Palmer, R.A. (1982) Acta Crystallogr. B38, 2210-2217], while in the protein-purine derivative the imidazole group is located in the major site. Inhibitor binding induces movements in the side-chains of Lys-7 and Lys-66 which also modify the conformation of the active-site cleft of ribonuclease A.
 ...
PMID:The active site of ribonuclease A from the crystallographic studies of ribonuclease-A-inhibitor complexes. 640 32

Lysozyme, ribonuclease and insulin were exposed to dry heating for 1 to 24 h at temperatures between 80 and 180 degrees C. Amino acid analyses of the heated samples showed that most of the amino acids are stable up to 120 degrees C. Initially, at higher temperatures, an almost rectilinear decrease took place which reached a critical stage at 160 degrees C. Nonpolar aliphatic, acidic and aromatic amino acids were all relatively stable (maximum loss less than 20% after 24 h at 180 degrees C). The lability of the other amino acids increased in the order proline, arginine, histidine, cysteine, threonine, lysine, tryptophan, serine, and methionine. Methionine was 86% decomposed after 24 h at 180 degrees C. Loss of trinitrobenzene sulfonic acid-reactive lysine ("available lysine") reached 20% at 100 degrees C and essentially 100% after 24 h at 180 degrees C. Maximum loss in weight during heating was 11%, although maximum protein loss was between 20 and 35%. Reaction orders and activation energies were estimated for some of the amino acid losses. Of the atypical amino acids ("hot spots") lysinoalanine, allo-isoleucine and ornithine that were detected, only lysinoalanine is useful as an indicator to detect amino acid damage after dry heating.
 ...
PMID:Model studies on the heating of food proteins. Amino acid composition of lysozyme, ribonuclease and insulin after dry heating. 641 75

The ability of dolichyl-P-P-oligosaccharide:peptide oligosaccharyltransferase to use exogenous substrates (a previously labeled oligosaccharide lipid and an Asn-X-Thr containing heptapeptide) is shown to require phospholipid. The enzyme was extracted from porcine thyroid rough microsomes using NaCl-Nonidet P-40. When measured at low concentration, in a neutral detergent-containing medium, it undergoes a rapid loss of activity, which renders impossible quantitative estimates in the range of 0-50 micrograms microsomal protein/50 microliters assay. We observed that inactivation could be prevented by supplementing the assay with a previously heat-treated suspension of microsomes in neutral detergent, or with the corresponding extract. Further investigation revealed that phospholipids are responsible for this enzyme stabilization, since phospholipase A2 and phospholipase C treatments were both able to abolish this effect. When individual phospholipids were compared for their protective efficiency, egg yolk phosphatidylcholine was found to be by far the most efficient. Phosphatidylglycerol, phosphatidylinositol and phosphatidylserine were only slightly effective, while phosphatidylethanolamine and lysophosphatidylcholine had no effect at all. Of those tested, partly unsaturated phosphatidylcholines with 16-18 carbon atom acyl chains were the most active, at an optimal concentration of 1-2 mM. Under these conditions a Km of 15 microM was measured for the acceptor, a synthetic ribonuclease heptapeptide, and a Km of 0.55 microM for the donor, dolichyl-P-P-GlcNAc2-Man9-Glc2-3. These findings were confirmed by subjecting a sodium deoxycholate extract to depletion of endogenous lipids by gel filtration. Enzyme activity was totally abolished and then restored (up to now only partially) by addition of phosphatidylcholine.
 ...
PMID:Phosphatidylcholine requirement for the N-glycosylation of synthetic peptides by detergent-solubilized oligosaccharyltransferase. 654 Jan 20

The amino acid sequences of the pancreatic ribonuclease from capybara (Hydrochoerus hydrochaeris) and cuis (Galea musteloides) were determined. Both species belong to the same superfamily of the hystricomorph rodents as the guinea-pig. In guinea-pig pancreas two ribonucleases are present as a result of a recent gene duplication, but in capybara and cuis pancreas only one single ribonuclease has been found. A most parsimonious tree of ribonucleases indicates that the gene duplication leading to both guinea-pig ribonucleases occurred before the divergence of guinea-pig from capybara and cuis. This would mean that changes in expression of the ribonuclease genes have occurred in these taxa. Cuis and capybara ribonuclease have no Asn-X-Ser/Thr sequences and are carbohydrate-free proteins. Capybara ribonuclease has leucine at position 114, a position occupied by proline in the cis-configuration in bovine pancreatic ribonuclease.
 ...
PMID:Origin of the duplicated ribonuclease gene in guinea-pig: comparison of the amino acid sequences with those of two close relatives: capybara and cuis ribonuclease. 657 Dec 19

The temperature (-7 degrees C to 45 degrees C, pH 5.4) and pH (0 degrees C) dependence of 1H chemical shifts of ribonuclease S-peptide (5 mM, 1 M NaCl) has been measured at 360 MHz. The observed variations evidence the formation of a partial helical structure, involving the fragment Thr-3-Met-13. Two salt-bridges stabilize the helix: those formed by Glu-9- ...His-12+ and Glu-2- ...Arg-10+. The structural features deduced from the 1H-NMR at low temperature for the isolated S-peptide are compatible with the structure shown by the same molecule in the ribonuclease S crystal.
 ...
PMID:Low-temperature 1H-NMR evidence of the folding of isolated ribonuclease S-peptide. 662 74

Circulating M antigen, specific for genus Schistosoma, was previously described in serum, urine, patients' milk, and in serum and urine of animals infected by S. mansoni. The M antigen was thermostable and soluble in trichloroacetic acid. It was not hydrolyzed by protease, ribonuclease, amylase, or neuraminidase but destroyed by sodium metaperiodate. In the present study, we have purified the M ag by using trichloroacetic acid solubility, DEAE Sephadex, and immunoadsorption. The M ag showed a neutral electric charge, a m.w. heterogeneity, and was only stained by periodic acid-Schiff. The composition study revealed M ag was a glycoprotein with a polysaccharide moiety (63% of the molecules) particularly rich in galactose, fucose, glucosamine, and mannose, and with a high molecular ratio of serine and threonine. The presence of O-glycosidic linkage allowed M ag to be considered as a mucin or a mucus glycoprotein-like component. It was localized in the cell wall of the gut of adult worms.
 ...
PMID:Purification, immunochemical, and biologic characterization of the Schistosoma circulating M antigen. 698 17

A procedure for the preparation of porcine protease E is described. The availability of a convenient source of the enzyme has permitted specificity studies utilizing the macromolecular substrates oxidized insulin A and B chains and oxidized ribonuclease. The results show that protease E has a pronounced selectivity for the carbonyl bonds of serine threonine, alanine, and valine residues, with the latter most favored. The specificity is complementary to that of the chymotrypsins and we suggest that this property is physiologically significant. The k3 and Km values for the substrates acetyl-trialanine methyl ester, succinyltrialanine p-nitroanilide and benzoylalanine methyl ester are comparable to those observed by others for porcine elastase. The specificity observed in the present work, however, indicates that protease E may best be regarded as a member of the chymotrypsin group of enzymes.
 ...
PMID:The specificity of porcine pancreatic protease E. 700 83


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>