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:3.1.27.4 (ribonuclease)
6,621 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

M protein was extracted from type 24, group A streptococci with pepsin at pH 5.8 and was further purified by ammonium sulfate precipitation, ribonuclease digestion, ion-exchange chromatography, and isoelectric focusing. The purified pepsin extract of M (pep M) protein was shown to be free of nontype-specific immunoreactivity in (a) complement fixation tests with heterologous M antiserum, (b) skin tests in normal adult guinea pigs, and (c) passive hemagglutination tests for the presence of lipoteichoic acid sensitizing or antigenic activity. The pep M24 was highly immunogenic; two of three rabbits developed opsonic antibody titers of 1:256 and the third a titer of 1:32 6 wk after a single injection of 100-pg doses of pep M24 emulsified in complete Freund's adjuvant. The antisera lacked nontype-specific antibodies and produced single precipitin lines in agar gel diffusion tests against crude HC1 extracts of the homologous M protein. Thus, the type-specific antigenic determinant(s) of type 24 M protein appears to be separable from immunotoxic, cross-reactive antigens without loss of immunogenicity in rabbits. The mobility of pep M24 upon electrophoresis in 10 percent sodium dodecyl sulfate pelyacrylamide gel was consistent with an average mol wt of 33,500 daltons. Amino acid analysis demonstrated a predominance of alanine, followed by glutamic acid, lysine, leucine, and aspartic acid. Pep M24 contained an estimated six to seven methionine residues and approximately ten phenylalanine residues per molecule. No other aromatic amino acids were detected. Automatic Edman degradation of pep M24 yielded the sequence of the first 29 amino acids (the amino terminal amino acid being valine) of the amino terminal region of the molecule. The detection of only one new amino acid at each step of Edman degradation confirmed the homogeneity of the purified pep M24.
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PMID:Purification and properties of M protein extracted from group A streptococci with pepsin: covalent structure of the amino terminal region of type 24 M antigen. 32 68

The size of the cavity around Ser68 of Escherichia coli ribonuclease HI was modulated by amino acid substitutions to examine the effects on the stability of the enzyme. Five mutant proteins, Ser68----Gly, Ser68----Ala, Ser68----Thr, Ser68----Val and Ser68----Leu, were constructed. Each of the mutant proteins exhibited at least 40% of the enzyme activity of the wild-type protein. The stabilities of the mutant proteins were determined from urea-denaturation and thermal-denaturation curves. Among the five mutations, only the Ser----Val mutation resulted in an increase in the stability of the enzyme. The melting temperature, tm, at pH 3.0 of the mutant protein Ser68----Val was increased by 1.9 degrees C. Its free-energy change of unfolding in the absence of urea, delta G(H2O), and the midpoint of the denaturation curve, [D]1/2, were also increased by 5.4 kJ/mol and 0.18 M, respectively. The increase in the stability of the enzyme is probably due to the filling of the cavity space around Ser68 by valine. However, the mutation of Ser68 to glycine or leucine residues resulted in a considerable decrease in stability. In these cases, some conformational changes occur, as suggested by the CD and 1H-NMR spectra of these mutant proteins.
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PMID:Effect of cavity-modulating mutations on the stability of Escherichia coli ribonuclease HI. 131 95

The tRNA-like structure of turnip yellow mosaic virus is known to be efficiently recognized and aminoacylated by valyl-tRNA synthetase. The present work reports domains in the isolated tRNA-like fragment (159 terminal nucleotides at the 3'-end of the two viral RNAs) in contact with purified yeast valyl-tRNA synthetase. These domains were determined in protection experiments using chemical and enzymatic structural probes. In addition, new data, re-enforcing the validity of the tertiary folding model for the native RNA, are given. In particular, at the level of the amino acid accepting arm it was found that the two phosphate groups flanking the three guanine residues of loop I are inaccessible to ethylnitrosourea. This is in agreement with a higher-order structure of this loop involving "pseudo knotting", as proposed by Rietveld et al. (1982). Valyl-tRNA synthetase efficiently protects the viral RNA against digestion by single-strand-specific S1 nuclease at the level of the anticodon loop. With cobra venom ribonuclease, specific for double-stranded regions of RNA, protection was detected on both sides of the anticodon arm and at the 5'-ends of loop I, a region that is involved in the building up of the acceptor arm. Loop II, which is topologically homologous to the T-loop of canonical tRNA was likewise protected. Weak protection was observed between arms I and II, and at the 3'-side of arm V. This arm, located at the 5'-side of arm IV (homologous to the D-arm of tRNA), does not participate in the pseudo-knotted model of the valine acceptor arm. Ethylnitrosourea was used to determine the phosphates of the tRNA-like structure in close contact with the synthetase. These are grouped in several stretches scattered over the RNA molecule. In agreement with the nuclease digestion results, protected phosphates are located in arms I, II, and III. Additionally, this chemical probe permits detection of other protected phosphates on the 3'-side of arm IV and on both sides of arm V. When displayed in the three-dimensional model of the tRNA-like structure, protected areas are localized on both limbs of the L-shaped RNA. It appears that valyl-tRNA synthetase embraces the entire tRNA-like structure. This is reminiscent of the interaction model of canonical yeast tRNAVal with its cognate synthetase.
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PMID:Contact areas of the turnip yellow mosaic virus tRNA-like structure interacting with yeast valyl-tRNA synthetase. 354 Mar 11

Kinetic constants for the transesterification of eight dinucleoside phosphates CpX and UpX by bovine and turtle pancreatic ribonuclease were determined. Both ribonucleases have a preference for purine nucleotides at the position X. However, bovine ribonuclease, like other mammalian ribonucleases, prefers 6-amino bases at this site, while turtle ribonuclease prefers 6-keto bases. This difference in specificity at the B2 site may be explained by the substitution of glutamic acid at position 111 by valine in turtle ribonuclease. These results have been confirmed by inhibition studies with the four nucleoside triphosphates. Inhibition studies with pT and pTp showed that a cationic binding group (P0) for the 5'-phosphate of the pyrimidine nucleotides bound at the primary B1 site is present in turtle ribonuclease, although lysine at position 66 in bovine ribonuclease is absent in turtle ribonuclease. However, the side chain of lysine 122 in turtle ribonuclease is probably located in the correct position to take over the role as cationic P0 site.
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PMID:Kinetic studies on turtle pancreatic ribonuclease: a comparative study of the base specificities of the B2 and P0 sites of bovine pancreatic ribonuclease A and turtle pancreatic ribonuclease. 375 85

1. An improved 11000g cell-free system for the incorporation of [(14)C]valine into gramicidin S has been obtained. The cell-free extract used was the supernatant obtained by treating Bacillus brevis with ultrasonics for 1min. followed by centrifugation at 11000g. The optimum pH for the incorporation was 8.2-8.4 and the optimum Mg(2+) concentration 0.05m. The presence of ammonium sulphate (0.1m) and K(+) (0.01m) increased the incorporation. 2. Cell-free extracts prepared from cells harvested in the early phase of growth (extinction value 0.1) incorporated negligible amounts of [(14)C]valine into gramicidin S compared with that incorporated by cell-free extracts prepared from cells harvested in the late phase of growth (extinction value 0.5). This was not due to the presence of inhibitors in the cell-free extracts prepared from cells harvested early, since there was no marked decrease in gramicidin S synthesis in a mixture of extracts prepared from cells harvested early and late in the growth phase. 3. The small incorporation of [(14)C]valine into protein, which took place in cell-free extracts from cells harvested in the late growth phase, was not inhibited by puromycin, chloramphenicol and ribonuclease. However, the substantial incorporation that took place in cell-free extracts prepared from cells harvested in the early phase of growth was completely inhibited by puromycin, chloramphenicol and ribonuclease. On mixing cell-free extracts prepared from cells harvested early and late in the growth phase, it appeared that the small incorporation that occurs in extracts from cells harvested in the late phase of growth was not due to cellular inhibitors.
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PMID:Further studies on the biosynthesis of gramicidin S and proteins in a cell-free system from Bacillus brevis. 602 14

1. After incorporation of [(14)C]valine in vitro, cerebral microsomes were separated into membrane-bound and free ribosomes by sucrose-density-gradient centrifugation. 2. In preparations from both 4-day-old and adult rats, free and bound ribosomes incorporated [(14)C]valine. Free ribosomes could be found as polysomes, which were highly active. 3. Microsomes labelled with [(14)C]valine in vitro were fractionated after deoxycholate treatment into a preliminary sediment, sedimented at 105000g (5min.), and ribonucleoprotein particles, sedimented at 150000g (70min.), to determine the role of membrane-bound ribosomes. In the adult the ribonucleoprotein particles retained most of the radioactivity, whereas in the young the preliminary sediment was as highly labelled as the ribonucleoprotein particles. 4. The labelled preliminary sediment from young preparations was both ribonuclease- and deoxycholate-resistant, and the nature of this material is discussed in terms of a possible structural component of microsomal membranes.
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PMID:Microsomal components in relation to amino acid incorporation by preparations from the developing rat brain. 603 14

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 effects of different intravenous nutritional regimens on a number of biochemical indices of nutritional status were studied during the 8-day period following severe trauma. The inclusion of large amounts of amino acids (high nitrogen (N) was shown to greatly improve N balance over an isocaloric regimen containing no amino acids (O g N). The concentration of serum albumin, transferrin, prealbumin, and retinol-binding protein all fell during the study period in both patient groups, whereas the serum concentrations of acute phase reactants and of ribonuclease increased in the two groups. The sum of plasma levels of branched-chain amino acids and the essential amino acids was increased to a greater extent in the high N group. These amino acid totals and the ratio of glycine/valine showed a significant correlation with N balance in this group. Despite the marked difference in N balance, 3-methylhistidine excretion was increased but equal in the two nutritional groups, suggesting an increased rate of muscle protein breakdown in both groups, which appears not to be influenced by amino acid nutrition. It is concluded that N balance can be significantly improved in the immediate posttrauma period by provision of amino acids together with energy substrates. None of the biochemical variables measured, with the exception of plasma levels of essential amino acids, reflected these marked differences in N balance.
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PMID:Biochemical changes associated with severe trauma. 677 18

The hydrolysis of several tRNAs by an endonuclease extracted from the venom of Naja oxiana and specific for double-stranded, or at least highly ordered, regions has been studied under various experimental conditions. It is shown that the hydrolysis patterns of yeast tRNAPhe, tRNAVal and tRNAAsp in the isolated state are similar, most of the cuts occurring in the anticodon and acceptor stems. Ionic conditions are able to modify the hydrolysis pattern. The origin of these modifications is discussed. The protection against ribonuclease action, afforded to tRNAPhe, tRNAVal and tRNAAsp by the cognate aminoacyl-tRNA synthetase, is analyzed. It is shown that in all cases the anticodon stem is protected. The 3'-terminal region does not seem to be tightly engaged in the complex with the aminoacyl-tRNA synthetase. These results are discussed in the light of information on contact areas previously obtained by ultraviolet cross-linking techniques. The effects of the small ligands (ATP and amino acid) on the protection afforded to the tRNA by the cognate synthetase, have been studied. In the valine and aspartic acid systems, ATP induced a modification of the tRNA-enzyme complex leading to differences in the hydrolysis pattern of the 3'-accepting region. The effects of aminoacylation on the cleavage of tRNAPhe, tRNAVal and tRNAAsp were also studied. Whereas no modification of the cleavage map was observed in the aspartic system, aminoacylation resulted in slight but significant modifications of the hydrolysis pattern for tRNAPhe and tRNaVal in the 3'-terminal region.
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PMID:Comparison of the hydrolysis patterns of several tRNAs by cobra venom ribonuclease in different steps of the aminoacylation reaction. 691 54

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.
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PMID:The specificity of porcine pancreatic protease E. 700 83


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