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:3.1.27.5 (RNase)
17,967 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The conformational properties of the ribonuclease C-terminal 112-124 fragment have been studied by CD and 1H- and 13C-NMR in an attempt to determine whether native secondary structure elements other than alpha-helices have stability enough to be detected when isolated in aqueous solution. Only sequential alpha N and intraresidue NOE cross-peaks are observed in the NOESY spectra, a fact which points towards an essentially extended polypeptidic chain. Observed spectral variations with temperature, pH and urea addition allowed the identification of two non-random regions within the chain. The first one is located within residues 119-121, the same region where a native salt bridge (H119...D121) exists in the native protein, and the stability of that structure is affected by the protonation state of carboxylate groups. The second one involves the S123 and V124 residues at the C-terminal end. No signs of the native 112-115 beta-turn were detected which suggests that, in contrast to alpha-helices, long range interactions may be needed to stabilize these secondary structure elements.
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PMID:Solution structure of the isolated ribonuclease C-terminal 112-124 fragment. 234 Feb 92

The solution structure of human U1 snRNA was investigated by using base-specific chemical probes (dimethylsulfate, carbodiimide, diethylpyrocarbonate) and RNase V1. Chemical reagents were employed under various conditions of salt and temperature and allowed information at the Watson-Crick base-pairing positions to be obtained for 66% of the U1 snRNA bases. Double-stranded or stacked regions were examined with RNase V1. The dat gained from these experiments extend and support the previous 2D model for U1snRNA. However, to elucidate some aspects of the solution data that could not be accounted for by the secondary structure model, the information gathered from structure probing was used to provide the experimental basis required to construct and to test a tertiary structure model by computer graphics modeling. As a result, U1 snRNA is shown to adopt an asymmetrical X-shape that is formed by two helical domains, each one being generated by coaxial stacking of helices at the U1 snRNA cruciform. Chemical reactivities and model building show that a few nucleotides, previously proposed to be unpaired, can form A.G and U.U non Watson-Crick base-pairs, notably in stem-loop B. The structural model we propose for regions G12 to A124 integrates stereochemical constraints and is based both on solution structure data and sequence comparisons between U1 snRNAs.
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PMID:Solution structure of human U1 snRNA. Derivation of a possible three-dimensional model. 237 9

Sera from patients with systemic autoimmune diseases often contain antibodies against small nuclear ribonucleoprotein (snRNP) particles. Anti-Sm antibodies react with the entire set of U1, U2, U4, U5 and U6 (U1-U6) RNP particles whereas anti-(U1)RNP sera specifically recognize particles containing U1 RNA. Here we performed semi-quantitative immunoblotting using 16 human anti-Sm, 15 human anti-(U1)RNP sera and two mouse monoclonal antibodies to establish which snRNA-associated proteins carry antigenic determinants. Almost every (15/16) human anti-Sm sera recognized epitopes present on a 28-kDa (B/B') protein doublet and on a 16-kDa (D) polypeptide. Nine anti-(U1)RNP sera also recognized the B/B' doublet, but in all cases a much stronger reaction was observed with one or more of the specifically U1 RNA-associated 70 kDa, A or C antigens. With affinity-purified antibody fractions eluted from individual antigen bands on nitrocellulose blots it is shown that the anti-Sm-reactive polypeptides B/B' and D contain common epitopes. We also report the finding of one human anti-Sm serum with exclusive specificity for the B/B' doublet and a mouse monoclonal anti-Sm antibody recognizing only the D protein, indicating that these antigens also carry unique epitopes. In immunoprecipitation assays, purified anti-B/B' and -D antibodies react with (U1-U6) RNP while purified anti-70 kDa, anti-A and anti-C antibodies precipitate exclusively U1 RNP particles. Finally, we established the subcellular localization of Sm and U1 RNP antigens using a biochemical cell fractionation procedure. Part of the 70 kDa and B/B' antigens were found in a nuclease and high salt-resistant nuclear substructure, usually referred to as nuclear matrix, while the A and D antigens could be extracted completely from HeLa nuclei by ribonuclease treatment and subsequent high salt extraction.
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PMID:Further characterization and subcellular localization of Sm and U1 ribonucleoprotein antigens. 241 12

The experimental conditions ensuring the possibility of isolation of nuclear matrices enriched and non-enriched in transcribed DNA sequences were investigated. It is demonstrated that extraction of nuclease treated nuclei with very low ionic strength solution executed before the high salt extraction destroys the apparent attachment of transcriptionally active DNA to the nuclear skeleton elements. On the contrary RNase treatment of nuclei was found to have no effect on distribution of active genes versus points of DNA attachment to the nuclear skeleton.
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PMID:[Association of transcription-active DNA fraction with the nuclear skeleton is altered during incubation of nuclei in solutions of low ionic strength]. 242 47

This study identifies an intermediate-sized androgen receptor and characterizes its relationship with the 9.1S and 4.4S receptor forms. Under low ionic conditions, at 2-4 degrees C, there exists a 9.1S (+/- 0.17) (n = 30) oligomeric form which does not bind to DNA. Under high ionic conditions, this form dissociates to a 4.4S (+/- 0.08) (n = 18) monomeric form. When the salt concentration is lowered, the 4.4S monomer converts to a species with an intermediate sedimentation coefficient of 7.7S (+/- 0.15) (n = 17) which binds to DNA. Unlike the 9.1S oligomer the 7.7S form is not maintained by sodium molybdate under high ionic conditions but rather dissociates to the 4.4S monomer. To determine whether these forms were associated with RNA, the 7.7S form was incubated with RNase A and analyzed by density gradient centrifugation. The 7.7S form was digested fully by RNase to the 4.4S monomer. The 7.7S form demonstrated a buoyant density of 1.2459 +/- 0.014 g/cm3 (n = 6) in metrizamide gradients, suggesting a ribonucleoprotein component. The sedimentation coefficient of the 9.1S form was unaffected by RNase. These data suggest that the intermediate 7.7S receptor form is composed of 4.4S monomer associated with a ribonucleoprotein molecule(s).
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PMID:Properties of an intermediate-sized androgen receptor: association with RNA. 243 28

The glucocorticoid receptor from rat liver cytosol prepared in 2 ml buffer/g tissue sedimented at approximately 10 S in low salt density gradient centrifugation without molybdate. When the receptor was heated at 25 degrees C, both approximately 10 S and approximately 7 S forms were seen in low salt gradient. The approximately 10 S form was not capable of binding to DNA-cellulose and was stabilized by sodium molybdate, namely it corresponded to untransformed receptor. The approximately 7 S form was capable of binding to DNA-cellulose and regarded as transformed receptor. On the other hand, partially-purified transformed receptor labeled with [3H]dexamethasone-21-mesylate sedimented at approximately 5 S, which migrated as a approximately 94 kDa species in SDS-polyacrylamide gel electrophoresis. The reconstitution analysis of this partially-purified approximately 5 S receptor and liver cytosol, showed the shift to approximately 7 S form. RNase A or T1 converted approximately 7 S transformed form into approximately 5 S but it did not affect approximately 10 S untransformed form. 5-20 mM sodium molybdate also shifted approximately 7 S to approximately 5 S. These results indicate that the approximately 7 S transformed form of the glucocorticoid receptor observed in low salt conditions might be an oligomer, probably including both approximately 5 S steroid-binding component and RNA/ribonucleoprotein, and that molybdate dissociates these interactions in a specific manner.
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PMID:Sodium molybdate converts the RNA-associated transformed, oligomeric form of the glucocorticoid receptor into the transformed, monomeric form. 244 Nov 43

The transformed androgen receptor from rat submandibular gland converts to a faster sedimenting form (6-8S) on a glycerol gradient centrifugation after withdrawal of a transformation-inducing reagent (KCl or ATP). In this report, the association of cytosolic RNA with the transformed androgen receptor was investigated as a possible mechanism of molecular conversion of the androgen receptor. When the transformed and converted androgen receptors were treated with RNase A, these receptors sedimented at 4.5S in a low-salt glycerol gradient. Addition of RNA from rat submandibular gland to the RNase-Sepharose-treated transformed receptor caused a shift of receptor peak from 4.5S to 5.8S. RNA from rat submandibular gland, yeast RNA and E. coli rRNA inhibited DNA-cellulose binding of a RNase-treated transformed receptor in the absence of molybdate. These observations suggest that conversion from the transformed 4S androgen receptor to a 6-8S form resulted from the association of RNA(s) with the transformed receptor.
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PMID:Ribonucleic acid association with androgen receptor from rat submandibular gland. 245 Feb 27

This review will concentrate on certain aspects of the nucleic acids of Entamoeba histolytica. Utilization and synthesis of purines and pyrimidines will initially be briefly discussed, e.g. salvage vs. de novo pathways, uptake studies and recognition of at least 4 transport loci. Data will be presented which show that the distribution and synthesis of RNA (to a lesser extent DNA) in the nucleus is basically the opposite one finds in other eukaryotes, viz. most RNA (ribosomal?) is synthesized (or accumulates) in the peripheral chromatin (functional equivalent of nucleolus?). The DNA is distributed and synthesized primarily throughout the nucleus. It is usually so dispersed that it will not stain with e.g. the standard Feulgen technique, unless the DNA condenses around the endosome (not a nucleolar equivalent) prior to nuclear division. Isolation of rRNA was difficult due, in part, to potent and difficult to inhibit RNase(s), some of which are apparently intimately bound to ribosomal subunits. The 25S (1.3 kDa), 17S (0.8 kDa) and 5S rRNA were recovered after isolation with a high salt SDS-DEP technique. This is the only procedure which enables us to obtain high yields of 25S rRNA; guanidine or guanidinium which permits isolation of intact functional mRNA results in isolation of small amounts of 25S RNA relative to 17S RNA. The 25S RNA is "nicked" (apparently during nuclear processing) and dissociates readily into 17S (0.7 kDa) and 16S (0.6 kDa) species, and a more rigidly bound 5.8S species. A small amount of "unnicked" 25S RNA was recovered with guanidine.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Nucleic acids of Entamoeba histolytica. 247 Sep

After exposure to ligand at 0-4 degrees C, estrogen receptors from mouse uteri characteristically eluted between thyroglobulin (Mr 669,000) and ferritin (Mr 443,000) during size-exclusion HPLC. However, when preparations were warmed with ligand under mild activating conditions, most or all of the receptor was observed as a much larger complex, which eluted between dextran blue 2000 and thyroglobulin. Formation of the large complex required ligand, was inhibited by molybdate, and occurred even in 0.4 M KCl. Slower ligand dissociation characterized the large complex, indicating that activated receptors were included preferentially. This large complex did not form when charged cytosols were aged, concentrated, or precipitated, indicating that formation was not the result of random aggregation. After exposure to conditions commonly used for activation (25 degrees C, 60 min), most receptor existed as a very large, monodisperse complex of finite size, predicting an ordered structure for these large complexes that should be useful for defining the types of proteins which can interact with estrogen receptors. Formation of the large complex was not impeded or disrupted by EDTA, RNase, DNase I, thiourea, or mercaptoethanol; however, the capacity to form this large complex was not demonstrated by preparations that had been exposed to trypsin or by the small receptor forms obtained after salt extraction. Proteolytic sensitivity and lack of sensitivity to RNase or DNase indicate that interactions between receptors and other proteins are involved in peak A formation.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Intermolecular engagement of estrogen receptors indicated by the formation of a high molecular weight complex during activation. 251 8

The C proteins (C1 and C2) of HeLa 40S heterogeneous nuclear ribonucleoprotein particles copurify under native conditions as a stable complex with a fixed molar protein ratio (S.F. Barnett, W.M. LeStourgeon, and D.L. Friedman, J. Biochem. Biophys. Methods 16:87-97, 1988). Gel filtration chromatography and velocity sedimentation analyses of these complexes revealed a large Stokes radius (6.2 nm) and a sedimentation coefficient of 5.8S. On the basis of these values and a partial specific volume of 0.70 cm3/g based on the amino acid composition, the molecular weight of the complex was calculated to be 135,500. This corresponds well to 129,056, the sequence-determined molecular weight of a (C1)3C2 tetramer. Reversible chemical cross-linking with dithiobis(succinimidyl propionate) and analysis of cross-linked and cleaved complexes in sodium dodecyl sulfate-polyacrylamide gel electrophoresis confirmed that the C proteins exist as tetramers, most or all of which are composed of (C1)3C2. The tetramer is stable in a wide range of NaCl concentrations (0.09 to 2.0 M) and is not dissociated by 0.5% sodium deoxycholate. This stability is not the result of disulfide bonds or interactions with divalent cations. The hydrodynamic properties of highly purified C-protein tetramers are the same for C-protein complexes released from intact particles with RNase or high salt. These findings support previous studies indicating that the core particle protein stoichiometry of 40S heterogeneous nuclear ribonucleoproteins is N(3A1-3A2-1B1-1B2-3C1-1C2), where N = 3 to 4, and demonstrate that the C-protein tetramer is a fundamental structural element in these RNA-packaging complexes. The presence of at least three tetramers per 40S monoparticle, together with the highly anisotropic nature of the tetramer, suggesting that one-third of the 700-nucleotide pre-mRNA moiety packaged in monoparticles is associated through a sequence-independent mechanism with the C protein.
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PMID:The C proteins of HeLa 40S nuclear ribonucleoprotein particles exist as anisotropic tetramers of (C1)3 C2. 256 30


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