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 three-dimensional structure of Ribonuclease St (RNase St), the extracellular ribonuclease from Streptomyces erythreus, has been deduced based on a preliminary electron density map at 2.5 A resolution. RNase St has a substrate specificity similar to ribonuclease T1 which catalyzes the splitting of the phosphodiester bond of guanylic acid. Crystals grown as diamond plates have space group C2 with unit cell parameters a=88.4, b=33.0, c=69.0 A, beta = 98.4 degrees having two enzyme molecules per asymmetric unit. Phases were obtained by use of KAu(CN)4, phenylmercuric acetate and UO2 (CH3COO)2. The overall dimensions of the molecule are 40 X 30 X 25 A. The most prominent secondary structural features are two turns of alpha-helix and a three strand stretch of antiparallel beta-sheet. The alpha-carbon backbone of RNase St seems to have no apparent correlation with that of ribonuclease A.
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PMID:Preliminary crystal structure analysis of a microbial, guanine-specific ribonuclease St at 2.5 A resolution. 679 45

The degradation of S--S bonds in 0.2 M-NaOH at 25 degrees C was studied for a series of proteins and simple aliphatic disulphide compounds, by using cathodic stripping voltammetry, ion-selective-electrode potentiometry, spectrophotometry and ultrafiltration. The disulphide bonds that dissociated in 0.2 M-NaOH were usually those that are solvent accessible and that can be reduced by mild chemical reductants. Some unexpected differences were found between similar proteins, both in the number of S--S bonds dissociated and in their rates of decomposition. Chymotrypsin has one S--S bond attacked, whereas chymotrypsinogen and trypsinogen have two. Ribonuclease A has two S--S bonds dissociated, but ribonuclease S and S-protein have three. Denaturation in 6 M-guanidine hydrochloride before alkaline digestion caused the loss of an additional S--S bond in ribonuclease A and insulin, and increased the rate of dissociation of the S--S bonds of some other proteins. The initial product of S--S bond dissociation in dilute alkali is believed to be a persulphide intermediate formed by a beta-elimination reaction. This intermediate is in mobile equilibrium with bisulphide ion, HS-, and decomposes at a mercury electrode or in acid solution to yield a stoichiometric amount of sulphide. Rate constants and equilibrium constants were measured for the equilibria between HS- and the intermediates involved in the alkaline dissociation of several proteins. Elemental sulphur was not detected in any of the protein digests. It is suggested that formation of HS- from a persulphide intermediate involves a hydrolysis reaction to yield a sulphenic acid derivative. The small polypeptides glutathione and oxytocin gave only a low yield of persulphide, and their alkaline decomposition must proceed by a mechanism different from that of the proteins.
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PMID:Degradation of protein disulphide bonds in dilute alkali. 721 43

Ribonuclease isolated from human urine is a glucoprotein of molecular weight 33,000. The purified enzyme inhibits: (1) the stimulation of 3H-thymidine uptake into lymphocytes by phytohemagglutinin, pokeweed, and concanavalin A; (2) the growth of pancreatic fibroblastoid cells in in vitro cell culture, and (3) the growth of colonies in bone marrow cell cultures. Ribonuclease levels in the uremic patient vary from 9,500 to 35,000 U/ml (normal 1,041 +/- 247). Serum ribonuclease levels are unaffected by dialytic procedures. It is suggested that the ribonuclease glycoprotein may represent a large number of nondialyzable high molecular weight uremic 'toxins'.
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PMID:Ribonuclease activity in renal failure. Evidence for toxicity. 726 14

Ribonuclease activity in the serum of patients with histologically confirmed ovarian carcinoma is significantly higher than in serum of patients with benign tumors of the ovary and that of healthy controls. In 847 samples collected during a period of 20 months the course of the ribonuclease activity of 41 patients receiving cytostatic treatment was determined. The ovarian carcinoma of all 41 patients was histologically ascertained. Three typical examples are presented.
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PMID:[Serum ribonuclease activity in gynecologic neoplasms. The behavior of serum ribonuclease in ovarian cancer under cytostatic therapy]. 746 46

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

An evaluation of the analytical performance of a method for determining ribonuclease catalytic activity employing digestion of RNA substrate was made. It was found that the relationship between concentrations of ribonuclease standards and concentrations of the reaction products, expressed as the 260 nm light absorbance values, was nonlinear and fulfils a binomial function. Substituting ribonuclease activities by square roots of ribonuclease activity values, a linear relationship with light absorbance values, ranging from 0.08 to 0.400 was obtained. In the present work one unit of ribonuclease catalytic activity was defined as RNA-degrading activity which in the assay conditions caused A260 equal to 0.332. The general equation of the ribonuclease catalytic activity was: Ribonuclease (U/l) = [(A260 - 0.02)/0.316]2. In spite of the nonlinearity of the standard curve, the actual CV values did not depend essentially on the value of measured activity and were estimated as 13%.
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PMID:Assessment of a method of determining ribonuclease activity employing RNA as substrate. 752 6

Ribonuclease mitochondrial RNA processing cleaves RNAs from the mammalian mitochondrial main non-coding regulatory region, called the displacement loop. Our data demonstrate that rat cells contain a site-specific ribonuclease mitochondrial RNA processing activity. We found that this enzyme processes the rat mitochondrial displacement-loop RNA substrate at the level of the conserved sequence block 1, a result which is different from that for mouse. This finding correlates with the in-vivo transcriptional analysis of the rat displacement-loop region. Processing by homologous and heterologous ribonuclease mitochondrial RNA enzymes occurs in the same manner, suggesting a conserved mode of substrate recognition.
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PMID:RNase mitochondrial RNA processing cleaves RNA from the rat mitochondrial displacement loop at the origin of heavy-strand DNA replication. 753 84

To elucidate a possible involvement of nitric oxide in the development of a mesangial proliferative glomerulonephritis induced by anti-Thy-1 antibody administration, glomerular expression of three isoforms of NO synthase (NOS), inducible NOS (iNOS), brain NOS, and endothelial NOS, was examined at both mRNA and protein levels by ribonuclease protection assay and immunofluorescence microscopy. Light microscopy showed an accumulation of polymorphonuclear leukocytes at 1 hour, lysis of mesangial cells at 1 day, a mesangial proliferative lesion at 4 to 10 days, and minimal residual glomerular lesions by 28 days. Ribonuclease protection assay showed that the glomerular expression of iNOS mRNA peaked at 1 hour and decreased thereafter. No substantial expression of iNOS mRNA was observed in normal glomeruli or in the nephritic glomeruli obtained at different time points (1, 4, 10, or 28 days). By immunofluorescence microscopy with a specific monoclonal antibody, an intense reaction for iNOS was demonstrated in a few cells in the glomeruli at 1 hour. Most of the iNOS-positive cells were identified as polymorphonuclear leukocytes. iNOS-positive cells were found less frequently in the glomeruli on days 1 and 4. Endothelial NOS mRNA was constitutively expressed in normal glomeruli and increased biphasically with two peaks at 1 hour and at 4 days or later; however, the peak expression was much less than that of iNOS mRNA at 1 hour. Expression of brain NOS mRNA was not detectable in either normal or nephritic glomeruli. These results show that iNOS is predominantly expressed in polymorphonuclear leukocytes accumulating at 1 hour in the glomeruli of anti-Thy-1 glomerulonephritis and suggest an involvement of NO in the initiation of the disease.
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PMID:Expression and localization of inducible nitric oxide synthase in anti-Thy-1 glomerulonephritis. 757 58

The actions of androgens in both peripheral and central tissues are linked in part to their ability to specifically bind and activate androgen receptors (ARs). ARs have been well studied in the rat hypothalamus and peripheral reproductive tissues, where they are directly involved in endocrine feedback mechanisms and reproduction. Previous studies revealed relatively high levels of AR and AR messenger RNA (mRNA) in the rat hippocampus; however, the action of androgen in this brain region remains unclear. To begin to address this issue, we used a multidisciplinary approach to quantitate hippocampal AR and AR mRNA levels and investigate their regulation after various hormonal manipulations. In vitro binding assays revealed a single, saturable, high affinity binding site for androgen in hippocampal cytosols. The expression of AR mRNA in the intact adult male rat hypothalamus and hippocampus was demonstrated using reverse transcription-polymerase chain reaction and quantified using a ribonuclease protection assay. Comparable levels of AR mRNA were found in the hippocampus and hypothalamus. In addition, in situ hybridization analysis revealed a unique distribution of AR mRNA in the hippocampus. AR mRNA was found predominately in the CA1 pyramidal cells, which form the major signal output of the hippocampal trisynaptic circuit. Reverse transcription-polymerase chain reaction of total RNA from microdissected hippocampal regions confirmed this distribution. Ribonuclease protection assay demonstrated a significant decrease in the AR mRNA content of the hippocampus in animals killed 4 days after castration or in intact rats after four daily injections of the AR antagonist, flutamide (15 mg/animal), compared to that in intact controls (P < 0.01). In contrast, a 35% increase (P < 0.05) in the hippocampal AR mRNA content was found in old (22-month-old) compared to young (5-month-old) male rats. In both cases, [3H]dihydrotestosterone binding to the cytosolic preparation did not parallel the changes observed in the AR mRNA content. Taken together, these data demonstrate that hippocampal cells containing AR can respond to circulating androgen to alter AR gene expression. Furthermore, AR mRNA autoregulation appears to be both age and tissue specific and does not directly follow the regulatory patterns described for other steroid hormone receptors found in the hippocampus.
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PMID:Distribution and hormonal regulation of androgen receptor (AR) and AR messenger ribonucleic acid in the rat hippocampus. 762 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


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