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)

Hydrogen exchange has been studied in a single crystal of RNase A [ribonuclease (pancreatic), EC 3.1.27.5] in the course of a neutron structure investigation. Refinement of the occupancies of amide hydrogens provided information about the kind of isotope present in each site and also provided estimates of the errors associated with the measurement. Twenty-eight of the 120 peptide amide hydrogens were found to be at least partially protected from exchange during approximately 1 year required for crystal preparation and data collection. Most of the protected hydrogens were involved in hydrogen bonds with main-chain carbonyl groups. A contiguous region of the beta-sheet containing residues 75, 106--109, 116, and 118 had a large number of protected hydrogens, indicating its low flexibility and the lack of accessibility to solvent. Residues 11--13 from the alpha-helix near the amino terminus were protected, in good agreement with a model of cooperative unwinding of this helix, starting from the free (amino) end.
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PMID:Hydrogen exchange in RNase A: neutron diffraction study. 695 Nov 86

Inhibitors of neutral ribonuclease have been purified to homogeneity from beef, pig, sheep, mouse, and rat liver by affinity chromatography on Sepharose-RNase A with overall yields ranging from 60-80%. Each of the purified inhibitors presents a single band by SDS-gel electrophoresis; molecular weight estimates by SDS-gel electrophoresis and by gel filtration are ca. 50 000. Each of the inhibitors forms a complex with beef pancreatic RNase A with a molecular weight of ca. 64 000, suggestive of 1:1 binding on a molar basis. The inhibitors from liver are very similar in properties and amino acid composition to the previously isolated inhibitor from human placenta (Blackburn et al. (1977) J. Biol. Chem. 252, 5904) and beef brain (Burton et al. (1980) Int. J. Peptide Protein Res. 16, 359). Pig liver offers an alternative to human placenta as a source for an RNase inhibitor of this type (yield, ca. 8 mg/kg of tissue). Immunological similarities were examined using antiserum directed against human placental RNase inhibitor. Cross reactivity of the liver RNase inhibitors with the antiserum raised against placental RNase inhibitor ranged from 15% for mouse RNase inhibitor to as low as 2% for pig and sheep RNase inhibitor.
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PMID:Ribonuclease inhibitors from the livers of five mammalian species. 711 7

A ribonuclease inhibitor from bovine brain has been purified 27 000-fold by affinity chromatography on Sepharose-RNase A with an overall yield of 46% (ca. 0.4 mg/kg tissue). The purified inhibitor gives a single band by SDS-gel electrophoresis. By gel filtration the molecular weight is ca. 50 000; the molecular weight of the complex with bovine pancreatic RNase A is ca. 62 000, indicative of 1:1 binding on a molar basis. The inhibition of the action of RNase A on yeast RNA by the inhibitor is noncompetitive with a Ki of 7 x 10(-10) M. The protein is very similar in its properties, including amino acid composition, to the inhibitor previously isolated from human placenta. The amount of inhibitor per g of protein in bovine brain is about one-seventh of the value for human placenta. No difference was found in the distribution of inhibitor between white and gray matter; one-tenth of the inhibitor present is bound to a brain ribonuclease which is released in active form after reaction with p-hydroxymercuribenzoate. Essentially no free neutral ribonuclease activity could be detected in brain homogenates in the absence of p-hydroxymercuribenzoate.
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PMID:Ribonuclease inhibitor from bovine brain. 721 11

A hybrid RNase S', consisting of synthetic S-peptide of rat ribonuclease and bovine S-protein, was studied by 1H n.m.r. to determine the effects of the many N-terminal amino acid replacements in rat S-peptide as compared to bovine S-peptide. As judged from the aromatic resonances, the conformation of the hybrid RNase S' is essentially identical to the conformation of bovine RNase S'. Notably, the active-site histidines 12 and 119 were not affected by the substitutions in the S-peptide, confirming earlier findings that the catalytic properties of naturally occurring RNases are modulated by the S-protein part of the molecule only. However, the resonances of Tyr-25 and His-48, which in RNase A are involved in a pH-dependent conformational transition, appeared to be different in the hybrid RNase, demonstrating that amino acid replacements may influence the structure of the protein locally.
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PMID:Nuclear magnetic resonance study of a hybrid of bovine and rat ribonuclease. 744 54

Ribonuclease Inhibitor (RI) has been purified from pig testis. It contains 30 half-cystines whose oxidation affects its ability to bind and inhibit ribonuclease (RNase). By N-terminal sequence analyses testis RI showed to be identical to that from porcine liver, for which a characteristic all-or-none type of SH-oxidation by 5,5'-dithiobis(2-nitrobenzoic acid) (DTNB) has been reported (Fominaya, J.M., and Hofsteenge, J. (1992) J. Biol. Chem. 257, 24655-24660). Under comparable reaction conditions, testis RI bound to RNase A did not exhibit this particular type of oxidation; instead, bound RI got intermediate oxidation degrees (up to 14 thiols oxidized per RI moiety) without dissociating from RNase. Moreover, RNase bound to partially oxidized RI was able to express some (15%) of its potential activity (active complex). Only when DTNB treatments accounted for complex dissociation (> 14 thiols oxidized per RI moiety) the released RI molecules exhibited the all-or-none oxidation behavior. By both kinetic and circular dichroism analyses, conformational changes have been evidenced for the transition from the inactive to the active form of RI-RNase complex. Relaxation of RI-RNase binding without major alterations in RI structure is proposed as responsible for complex activation. The results are discussed in terms of a model for the reversible regulation of RNase activity mediated by the redox status of RI.
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PMID:Thiol-disulfide exchange of ribonuclease inhibitor bound to ribonuclease A. Evidence of active inhibitor-bound ribonuclease. 749 72

Ribonucleases are widely found on the tissues of living organisms, but the functions of individual ribonucleases are not clear. To facilitate characterization of individual ribonucleases, I have developed a rapid method to separate and identify each ribonuclease from a crude sample by gel electrophoresis instead of by time-consuming purification steps. The ribonucleases in a crude sample are first separated by RNA-cast SDS-polyacrylamide gel electrophoresis and then eluted from the gel after ethidium bromide staining. To determine the base specificity of each ribonuclease, a 5' labelled oligonucleotide with known sequence is added to the enzyme eluate and the digested products are analyzed by denaturing gel electrophoresis. The base specificity of bovine pancreatic ribonuclease (RNase A), bullfrog oocyte-specific ribonuclease (RC-RNase), human serum ribonucleases and sweet potato leaf ribonucleases were determined by this method. Other properties of individual ribonucleases, e.g. substrate preference, may also be determined from crude samples by this method without further purification steps.
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PMID:Determination of base specificity of multiple ribonucleases from crude samples. 756 55

Angiogenin, a member of the pancreatic-like ribonuclease family with a special biological action (RISBAses), is a basic protein that induces blood vessel formation. Another member of these special ribonucleases, bovine seminal ribonuclease (BS RNase), displays biological properties, including aspermatogenic, embryotoxic, antitumor and immunosuppressive activities. The effects of two angiogenin preparations tested on the biological activities mentioned above are reported and compared with those of BS RNase and RNase A. In contrast to RNase A, which was ineffective in all biological activities tested, angiogenin suppressed significantly the proliferation of human lymphocytes stimulated by phytohemagglutinin or concanavalin A or by allogenic human lymphocytes (mixed lymphocyte culture). However, angiogenin did not affect the growth of human tumor cell lines, development of cow and mouse embryos and spermatogenicity in mice. On the basis of these results, angiogenin is the first monomeric ribonuclease described so far that displays immunosuppressive activity similar to that of the dimeric BS RNase. The immunosuppressive activity of angiogenin might synergize with the effect on neovascularization of tumor tissues and thus contribute to the development of tumor.
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PMID:Immunosuppressive activity of angiogenin in comparison with bovine seminal ribonuclease and pancreatic ribonuclease. 758 54

Bovine seminal ribonuclease (BS-RNase), a homolog of bovine pancreatic ribonuclease (RNase A), is isolated as a dimer in which the subunits are cross-linked by two disulfide bonds. In addition to this anomalous quaternary structure, the enzyme has extraordinary biological properties, such as antispermatogenic, antitumor, and immunosuppressive activities. The molecular bases for these properties are well-suited for exploration with the techniques of recombinant DNA. Accordingly, a gene encoding BS-RNase was designed based on criteria expected to maximize the translational efficiency of its mRNA in Escherichia coli. This gene was constructed from 12 synthetic oligonucleotides and expressed with the phage T7 system. The protein thus produced was insoluble and accumulated under optimal conditions to 15% of total cellular protein or 200 mg/liter of culture. Ribonuclease activity was generated by air oxidation of the reduced and denatured protein. Three forms of active BS-RNase were isolated by gel filtration chromatography: the well-characterized dimer and monomer and a previously uncharacterized form that migrated as a trimer. The ribonuclease activities of all three forms were equivalent to or higher than that of dimeric BS-RNase isolated from bull seminal plasma.
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PMID:Bovine seminal ribonuclease produced from a synthetic gene. 768 24

There is a considerable degree of ambiguity in the literature regarding the role of the 2',3'-cyclic phosphodiesters formed during the reaction of RNA cleavage catalysed by ribonuclease. Usually the reaction is considered to take place in two steps: in the first step there is a transphosphorylation of the RNA 3',5'-phosphodiester bond broken yielding a 2',3'-cyclic phosphodiester which in the second step is hydrolysed to a 3'-nucleotide. Although in many occasions, either explicitly or implicitly, the reaction is treated as taking place sequentially, this is not the case as it has been shown that the 2',3'-phosphodiesters are actually released to the medium as true products of the reaction and that no hydrolysis of these cyclic compounds takes place until all the susceptible 3',5'-phosphodiester bonds have been cyclised. Comparison of the hydrolysis and alcoholysis of the 2',3'-phosphodiesters catalysed by RNase A indicates that the hydrolysis reaction has to be considered formally as a special case of the transphosphorylation back reaction in which the R group of the R-OH substrate is just H. It is thus concluded that the 2',3'-cyclic phosphodiesters formed in the ribonuclease A reaction are true products of the transphosphorylation reaction and not intermediates as usually considered.
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PMID:The role of 2',3'-cyclic phosphodiesters in the bovine pancreatic ribonuclease A catalysed cleavage of RNA: intermediates or products? 769 11

The X-ray structure of the ribonuclease inhibitor from porcine pancreas shows a remarkable non-globular fold. It possesses a large central hole that forms part of the RNase A binding site.
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PMID:'Holy' proteins. I: Ribonuclease inhibitor. 771 83


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