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:3.1.27.1 (RNase)
16,360 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Studies on the covalent structure of eland (Taurotragus oryx) pancreatic ribonuclease have been performed on tryptic and thermolysin digests. The first 45 residues have been determined with a Beckman sequencer. From the remaining part of the sequence only those peptides were sequenced that differed in amino acid composition with the corresponding peptide of bovine ribonuclease. Eland pancreatic ribonuclease differs in four positions from bovine pancreatic ribonuclease A, but more differences due to a different state of amidation may be present. The absence of an Asn-X-Thr/Ser sequence in the covalent structure of eland ribonuclease (asparagine 34 has been substituted by aspartic acid) explains the absence of a glycosidated component in eland ribonuclease.
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PMID:Studies on the covalent structure of eland pancreatic ribonuclease. 126 25

Assignment of most of the proton NMR resonances of bovine pancreatic RNase B has been achieved using standard NMR techniques and by comparison with the published assignments for RNase A. A comparison of the NMR spectra of RNase B with RNase A shows that glycosylation of the enzyme has little overall effect on the conformation of the protein in solution. Comparisons of hydrogen-deuterium solvent exchange rates for the NH protons of RNase A and RNase B were made using two-dimensional 1H correlation spectroscopy. In the case of the glycosylated enzyme the exchange rates decreased for the NH protons of residues 9-14, 23-24, 32, 34-35, 39-40, 43-44, 48-49, 60, 71, 75-76, 80, 83-85, 100-101, 107, 111 and 122, relative to the unglycosylated RNase A. These results are consistent with the presence of the oligosaccharide inducing enhanced global dynamic stability and consequent changes to the unfolding equilibrium of the enzyme. The enhanced stability is observed not only for residues in the vicinity of the glycosylation site, asparagine-34, but also at residues remote from this site, as much as 30 A away.
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PMID:Effects of glycosylation on protein conformation and amide proton exchange rates in RNase B. 132 37

Non-glycine residues with positive theta-angles have been identified in four proteins, barley serine proteinase inhibitor CI-2, bacterial ribonuclease (barnase) of Bacillus amyloliquefaciens, hen egg white lysozyme and a basic protein from barley seed (barwin) by use of nuclear magnetic resonance spectroscopy. By accurate measurements of the coupling constant (3)JHNHalpha and integration of the nuclear Overhauser HN-Halpha cross peak, positive theta-angles could be determined reliably to 60 degrees +/- 30 degrees, in full agreement with the crystal structures for lysozyme, barnase and serine proteinase inhibitor CI-2. The work emphasizes that positive theta-angles can also occur in non-glycine residues and in the four proteins, positive theta-angles have been observed for the residue types aspartic acid, asparagine, arginine, serine, glutamine, histidine, tyrosine, tryptophan and phenylalanine. The measured (3)JHNHalpha coupling constants and the intensity of the intraresidue HN-Halpha NOEs agree well with the solution structures of three of the proteins, using the existing parametrization of the Karplus curve (Pardi, A., Billeter, M. and Wuthrich, K. (1984) J. Mol. Biol., 180, 741-751; Ludvigsen, S. Andersen, K.V. and Poulsen, F.M. (1991) J Mol. Biol., 217, 731-736).
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PMID:Positive theta-angles in proteins by nuclear magnetic resonance spectroscopy. 139 67

The human immunodeficiency virus 1 (HIV-1) reverse transcriptase (RT) is a protein of 66 kDa, p66, which contains two domains, an amino-terminal DNA polymerase and an RNase H at the carboxy terminus of the molecule. In order to characterize the mode of action of the RNase H, two previously described mutant enzymes were used, with substitutions in the highly conserved histidine 539, which was mutated to the neutral amino acid asparagine and to the negatively charged aspartate. The purified wild-type (wt) and mutant (mt) enzyme activities are analyzed here using RNA-DNA hybrids consisting of in vitro transcribed RNA that harbors the polypurine tract (PPT) from HIV-1 and DNA oligonucleotides complementary to the PPT or to other regions of the RNA. Analysis of the radioactively labeled RNA of these model hybrids after RNase H treatment indicates that both, wt and mt enzymes, are capable of cleaving the RNA in an endonucleolytic manner. The mt enzymes exhibit a severely reduced exonuclease activity. They are more sensitive towards salt and competition with excess of unlabeled hybrid, suggesting a reduced substrate binding affinity. DNA elongation by the RT is coupled with RNA hydrolysis by the 3'-5' exonuclease of the wt RNase H. The RNase Hmt of the mt enzymes, however, does not exhibit such processive 3'-5' exonuclease activity during DNA synthesis but gives rise to sporadic endonucleolytic cuts, whereas the RT is not affected. The endonuclease activities of the RNase H mt enzymes exhibit cleavage preferences in the absence or presence of DNA synthesis different from those of the wt enzyme. They cannot recognize specific sequences required to generate a PPT-primer and therefore cannot initiate plus-strand DNA synthesis in vitro at the 3' end of the PPT, which is essential for viral replication.
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PMID:Mutations of a conserved residue within HIV-1 ribonuclease H affect its exo- and endonuclease activities. 171 5

Recombinant A' protein could be reconstituted into U2 small nuclear ribonucleoprotein particles (snRNPs) upon addition to HeLa cell extracts as determined by coimmunoprecipitation and particle density; however, direct binding to U2 RNA could not be demonstrated except in the presence of the U2 snRNP B" protein. Mutational analysis indicated that a central core region of A' was required for particle reconstitution. This region consists of five tandem repeats of approximately 24 amino acids each that exhibit a periodicity of leucine and asparagine residues that is distinct from the leucine zipper. Similar leucine-rich (Leu-Leu motif) repeats are characteristic of a diverse array of soluble and membrane-associated proteins from yeasts to humans but have not been reported previously to reside in nuclear proteins. Several of these proteins, including Toll, chaoptin, RNase/angiogenin inhibitors, lutropin-choriogonadotropin receptor, carboxypeptidase N, adenylyl cyclase, CD14, and human immunodeficiency virus type 1 Rev, may be involved in protein-protein interactions. Our findings suggest that in cell extracts the Leu-Leu motif of A' is required for reconstitution with U2 snRNPs and perhaps with other components involved in splicing through protein-protein interactions.
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PMID:Leucine periodicity of U2 small nuclear ribonucleoprotein particle (snRNP) A' protein is implicated in snRNP assembly via protein-protein interactions. 182 47

A semisynthetic RNase, RNase-(1-118).(111-124), consisting of a noncovalent complex between residues 1-118 of RNase (obtained from the proteolytic digestion of RNase A), and a synthetic 14-residue peptide containing residues 111-124 of RNase, exhibits 98% of the enzymatic activity of bovine pancreatic ribonuclease A (EC 3.1.27.5). The replacement of aspartic acid-121 by asparagine in this semisynthetic RNase to form the "D121N" analog reduces kcat/Km to 2.7% of the value for RNase A. In the present work, 1H NMR spectroscopy has been used to probe the ionization states of His12, His105, and His119 in this catalytically defective semisynthetic RNase. A comparison of the observed resonances of D121N with those previously determined by others for RNase A enabled us to assign the C2 proton NMR resonances to individual residues; the assignment of His119 was confirmed by titrating D121N with the fully deuterated peptide, [Asn121]-RNase-(111-124). The observed pKa values of His12, His105, and His119 decrease 0.18, 0.16, and 0.02 pH unit, respectively, as a result of the D121N replacement. Values calculated by using a finite difference algorithm to solve the Poisson-Boltzmann equation (the DELPHI program, version 3.0) and a refined 2.0-A coordinate set for the crystal structure of D121N differ significantly for active site residues His12 (delta pKa = -0.58) and His119 (delta pKa = -0.55) but not for His105 (delta pKa = -0.10). The elmination of bound water from the calculations reduced, but did not reconcile, these discrepancies (His12, delta pKa = -0.36; His119, delta pKa = -0.41).
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PMID:Histidine pKa shifts accompanying the inactivating Asp121----Asn substitution in a semisynthetic bovine pancreatic ribonuclease. 189 58

The complete primary structure of a base non-specific and adenylic acid preferential RNase (RNase M) from Aspergillus saitoi was determined. The sequence was determined by analysis of the peptides generated by digestion of heat-denatured RNase M with lysylendopeptidase, and the peptides generated from RCM RNase M by digestion with staphylococcal V8 protease or chemical cleavage with BrCN. It consisted of 238 amino acid residues and carbohydrate moiety attached to the 74th asparagine residue. The molecular weight of the protein moiety deduced from the sequence was 26,596. The locations of 10 half cystine residues are almost superimposable on those of RNase Rh from Rhizopus niveus and RNase T2 from Aspergillus oryzae which have similar base specificity. The homology between RNase M and RNase Rh and RNase T2 amounted to 97 and 160 amino acid residues, respectively. The amino acid sequences conserved in the three RNases are concentrated around the three histidine residues, which are supposed to form part of the active sites of these RNases.
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PMID:Primary structure of a base non-specific and adenylic acid preferential ribonuclease from Aspergillus saitoi. 222 29

The asparagine-linked sugar chains of bovine brain ribonuclease were quantitatively released as oligosaccharides from the polypeptide backbone by hydrazinolysis. After N-acetylation, they were converted into radioactively-labeled oligosaccharides by NaB3H4 reduction. The radioactive oligosaccharide mixture was fractionated by ion-exchange chromatography, and the acidic oligosaccharides were converted into neutral oligosaccharides by sialidase digestion. The neutral oligosaccharides were then fractionated by Bio-Gel P-4 column chromatography. Structural studies of each oligosaccharide by sequential exoglycosidase digestion in combination with methylation analysis revealed that bovine brain ribonuclease showed extensive heterogeneity. It contains bi- and tri-antennary, complex-type oligosaccharides having alpha-D-Manp-(1----3)-[alpha-D-Manp-(1----6)]-beta-D-Manp -(1----4)-beta-D- GlcpNAc-(1----4)-[alpha-L-Fucp-(1----6)]-D-GlcNAc as their common core. Four different outside oligosaccharide chains, i.e., beta-D-Galp-(1----4)-beta-D-GlcpNAc-(1----, alpha-Neu5Ac-(2----6)-beta-D- Galp-(1----4)-beta-D-GlcpNAc-(1----, alpha-Neu5Ac-(2----3)-beta-D-Galp-(1----4)- beta-D-GlcpNAc-(1----, and alpha-D-Galp-(1----3)-beta-D-Galp-(1----4)-beta-D-GlcpNAc-(1----, were found. The preferential distribution of the alpha-D-Galp-(1----3)-beta-D-Galp-(1----4)-beta-D-GlcpNAc group on the alpha-D-Manp-(1----6) arm is a characteristic feature of the sugar chains of this enzyme.
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PMID:The structure of the asparagine-linked sugar chains of bovine brain ribonuclease. 233 5

The amino acid sequence of a nonsecretory ribonuclease isolated from human urine was determined except for the identity of the residue at position 7. Sequence information indicates that the ribonucleases of human liver and spleen and an eosinophil-derived neurotoxin are identical or very closely related gene products. The sequence is identical at about 30% of the amino acid positions with those of all of the secreted mammalian ribonucleases for which information is available. Identical residues include active-site residues histidine-12, histidine-119, and lysine-41, other residues known to be important for substrate binding and catalytic activity, and all eight half-cystine residues common to these enzymes. Major differences include a deletion of six residues in the (so-called) S-peptide loop, insertions of two, and nine residues, respectively, in three other external loops of the molecule, and an addition of three residues at the amino terminus. The sequence shows the human nonsecretory ribonuclease to belong to the same ribonuclease superfamily as the mammalian secretory ribonucleases, turtle pancreatic ribonuclease, and human angiogenin. Sequence data suggest that a gene duplication occurred in an ancient vertebrate ancestor; one branch led to the nonsecretory ribonuclease, while the other branch led to a second duplication, with one line leading to the secretory ribonucleases (in mammals) and the second line leading to pancreatic ribonuclease in turtle and an angiogenic factor in mammals (human angiogenin). The nonsecretory ribonuclease has five short carbohydrate chains attached via asparagine residues at the surface of the molecule; these chains may have been shortened by exoglycosidase action.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Amino acid sequence of the nonsecretory ribonuclease of human urine. 316 97

Two glycopeptide hydrolases, an endo-beta-N-acetylglucosaminidase and peptide:N-glycanase (amidase), have been isolated from defatted jack bean meal by standard procedures involving differential solubility and column chromatography. The purified products appear to be free of contaminating proteases and exoglycosidases, and their substrate specificity has been explored with regard to both glycan and peptide structure of the substrates. The endoglycosidase appears to be specific for high mannose glycans; no hydrolysis of either hybrid or complex glycans has been observed. It shows limited activity with two intact glycoproteins, ribonuclease B and yeast invertase, and gives optimal rate with glycopeptides. Free glycan-Asn derivatives are poor substrates in comparison with glycopeptides or glycan-Asn derivatives where the alpha-amino group has been dansylated. The amidase will liberate both high mannose, hybrid, and asialo-complex glycans from both proteins and peptides, but many glycans in intact proteins or in long peptides are resistant to the amidase and become active as substrates only after further proteolytic cleavage. The best substrates appear to be those with the glycosylated asparagine no more than 4-5 residues in from either the NH2- or COOH-terminal end of the peptide. Sialylated glycans do not appear to be released by the amidase.
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PMID:Purification and characterization of two glycopeptide hydrolases from jack beans. 333 94


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