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)

In this work, the helix-forming residues in fragments of several proteins (ribonuclease, thermolysin, tendamistat and angiogenin) were identified by NOE and the helix proton shifts were measured as delta changes associated with helix-population increments driven by trifluoroethanol addition. When estimated in this way, a regular pattern of helix conformational shifts was clearly seen in the delta delta versus sequence profiles of all the peptides studied. The helix periodicity of the H alpha and H beta resonances was especially clear, an observation that earlier statistical studies of protein delta values failed to predict. Amide protons showed the largest helix shifts, but with a less-sharply defined periodic character. Aromatic residues considerably distorted the periodicity of the helix amide shifts in some peptides, as evidenced by the delta shifts of a RNase A fragment 1-15 analog in which the two aromatic residues were replaced by Ala. The relationship between helix periodicity and peptide amphiphatic character is discussed.
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PMID:Periodic properties of proton conformational shifts in isolated protein helices. An experimental study. 162 61

The crystal structure of RNase Rh, a new class of microbial ribonuclease from Rhizopus niveus, has been determined at 2.5 A resolution by the multiple isomorphous replacement method. The crystal structure was refined by simulated annealing with molecular dynamics. The current crystallographic R-factor is 0.200 in the 10-2.5 A resolution range. The molecular structure which is completely different from the known structures of RNase A and RNase T1 consists of six alpha-helices and seven beta-strands, belonging to the alpha+beta type structure. Two histidine and one glutamic acid residues which were predicted as the most probably functional residues by chemical modification studies are found to be clustered. The steric nature of the active site taken together with the relevant site-directed mutagenesis experiments (Irie et al.) indicates that: (i) the two histidine residues are the general acid and base; and (ii) an aspartic acid residue plays a role of recognizing adenine moiety of the substrate.
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PMID:Crystal and molecular structure of RNase Rh, a new class of microbial ribonuclease from Rhizopus niveus. 163 75

The eosinophil cationic protein (ECP), a potent helminthotoxin with considerable neurotoxic activity, was recently shown to also have ribonucleolytic activity. In this work the substrate preference of ECP ribonuclease action was studied in detail. With single-stranded RNA or synthetic polyribonucleotide substrates ECP showed significant but low activity, 70- to 200-fold less than that of bovine RNase A. ECP hydrolyzed RNA more rapidly than it did any synthetic polynucleotide. Poly(U) was degraded more rapidly than poly(C), and poly(A) and double-stranded substrates were extremely resistant. Defined low molecular weight substrates in the form of the 16 dinucleoside phosphates (NpN') and uridine and cytidine 2',3'-cyclic phosphates were tested, and none showed hydrolysis by ECP at a significant rate. The results link ECP ribonucleolytic activity to the 'non-secretory' liver-type enzymes rather than to the 'secretory' pancreatic-type RNases.
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PMID:Ribonuclease activity and substrate preference of human eosinophil cationic protein (ECP). 171 91

A comparison of the sequences of three homologous ribonucleases (RNase A, angiogenin and bovine seminal RNase) identifies three surface loops that are highly variable between the three proteins. Two hypotheses were contrasted: (i) that this variation might be responsible for the different catalytic activities of the three proteins; and (ii) that this variation is simply an example of surface loops undergoing rapid neutral divergence in sequence. Three hybrids of angiogenin and bovine pancreatic ribonuclease (RNase) A were prepared where regions in these loops taken from angiogenin were inserted into RNase A. Two of the three hybrids had unremarkable catalytic properties. However, the RNase A mutant containing residues 63-74 of angiogenin had greatly diminished catalytic activity against uridylyl-(3'----5')-adenosine (UpA), and slightly increased catalytic activity as an inhibitor of translation in vitro. Both catalytic behaviors are characteristic of angiogenin. This is one of the first examples of an engineered external loop in a protein. Further, these results are complementary to those recently obtained from the complementary experiment, where residues 59-70 of RNase were inserted into angiogenin [Harper and Vallee (1989) Biochemistry, 28, 1875-1884]. Thus, the external loop in residues 63-74 of RNase A appears to behave, at least in part, as an interchangeable 'module' that influences substrate specificity in an enzyme in a way that is isolated from the influences of other regions in the protein.
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PMID:A hybrid of bovine pancreatic ribonuclease and human angiogenin: an external loop as a module controlling substrate specificity? 179 6

Substantial evidence indicates that HIV-1 trans-activation by tat protein is mediated through the TAR RNA element. This RNA forms a stem-loop structure containing a three-nucleotide bulge and a six-nucleotide loop. Previous mutagenic analysis of TAR indicates that the bulge residues and a 4 bp segment of the stem constitute, in part, the tat binding site. However, there appears to be no sequence-specific contribution of the six-base loop. We have employed a ribonuclease protection technique to explore the interaction of tat with single-stranded regions of TAR. The results indicate that tat interacts with both the bulge and loop regions of TAR. Treatment of TAR RNA with RNase A results in cleavage at U23 and U31, located in the bulge and loop regions, respectively. High concentrations (approximately 2 microM) of Escherichia coli derived tat protein, prepared by standard procedures, gave complete protection of TAR RNA from RNase A cleavage. However, under these conditions, truncated TAR derivatives in which no stem-loop structure is expected to form were also protected, indicating nonspecific binding. In order to obtain a tat preparation with enhanced specificity toward TAR RNA, methods were developed for refolding the recombinant protein. This treatment enhanced the affinity of tat for TAR by approximately 30-fold [Kd(apparent) less than 25 nM] and markedly increased its specificity for the TAR. Again, tat protected TAR RNA from RNase A cleavage at both U23 and U31. Protection was also observed with RNase T1 which cleaves TAR RNA at three G residues in the six-base loop.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Refolded HIV-1 tat protein protects both bulge and loop nucleotides in TAR RNA from ribonucleolytic cleavage. 186 81

Pancreatic RNase injected into Xenopus oocytes abolishes protein synthesis at concentrations comparable to the toxin ricin yet has no effect on oocyte protein synthesis when added to the extracellular medium. Therefore RNase behaves like a potent toxin when directed into a cell. To explore the cytotoxic potential of RNase toward mammalian cells, bovine pancreatic ribonuclease A was coupled via a disulfide bond to human transferrin or antibodies to the transferrin receptor. The RNase hybrid proteins were cytotoxic to K562 human erythroleukemia cells in vitro with an IC50 around 10(-7) M whereas greater than 10(-5) M native RNase was required to inhibit protein synthesis. Cytotoxicity requires both components of the conjugate since excess transferrin or ribonuclease inhibitors added to the medium protected the cells from the transferrin-RNase toxicity. Compounds that interfere with transferrin receptor cycling and compartmentalization such as ammonium chloride decreased the cytotoxicity of transferrin-RNase. After a dose-dependent lag period inactivation of protein synthesis by transferrin-RNase followed a first-order decay constant. In a clonogenic assay that measures the extent of cell death 1 x 10(-6) M transferrin-RNase killed at least 4 logs or 99.99% of the cells whereas 70 x 10(-6) M RNase was nontoxic. These results show that RNase coupled to a ligand can be cytotoxic. Human ribonucleases coupled to antibodies also may exhibit receptor-mediated toxicities providing a new approach to selective cell killing possibly with less systemic toxicity and importantly less immunogenicity than the currently employed ligand-toxin conjugates.
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PMID:Cytotoxic potential of ribonuclease and ribonuclease hybrid proteins. 193 62

The interactions of human placental ribonuclease inhibitor (PRI) with bovine pancreatic ribonuclease (RNase) A and human angiogenin, a plasma protein that induces blood vessel formation, have been characterized in detail in earlier studies. However, studies on the interaction of PRI with the RNase(s) indigenous to placenta have not been performed previously, nor have any placental RNases been identified. In the present work, the major human placental RNase (PR) was purified to homogeneity by a five-step procedure and was obtained in a yield of 110 micrograms/kg of tissue. The placental content of angiogenin was also examined and was found to be at least 10-fold lower than that of PR. On the basis of its amino acid composition, amino-terminal sequence, and catalytic properties, PR appears to be identical with an RNase previously isolated from eosinophils (eosinophil-derived neurotoxin), liver, and urine. The apparent second-order rate constant of association for the PR.PRI complex, measured by examining the competition between PR and angiogenin for PRI, is 1.9 X 10(8) M-1 s-1. The rate constant for dissociation of the complex, determined by HPLC measurement of the rate of release of PR from its complex with PRI in the presence of a scavenger for free PRI, is 1.8 X 10(-7) s-1. Thus the Ki value for the PR.PRI complex is 9 X 10(-16) M, similar to that obtained with angiogenin, and 40-fold lower than that measured with RNase A. Complex formation causes a small red shift in the protein fluorescence emission spectrum, with no significant change in overall intensity. The fluorescence quantum yield of PR and the Stern-Volmer constant for fluorescence quenching by acrylamide are both high, possibly due to the presence of an unusual posttranslationally modified tryptophan residue at position 7 in the primary sequence.
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PMID:Interaction of human placental ribonuclease with placental ribonuclease inhibitor. 199 83

The present study evaluated serum ribonuclease activity (SRA) in patients with inflammatory and neoplastic pancreatic diseases. RNase determination was carried out using t-RNA (T) from E. coli MRE 600 at pH 7.4 and polycytidylic acid (poly-C) (P) at pH 6.6 as RNA substrates with RNase A from bovine pancreas as reference enzyme. Healthy volunteers had a SRA of T: 160 +/- 12 and P: 482 +/- 24 ngeq/mL (mean +/- SEM (n]. In patients with acute interstitial pancreatitis (AIP), SRA was similar to healthy controls (T: 166 +/- 14; P: 474 +/- 30 ngeq/mL). Patients with acute necrotizing pancreatitis (ANP) had increased SRA (T: 278 +/- 49; P: 791 +/- 145 ngeq/mL, p less than 0.01, compared to controls). SRA values were also increased in patients with chronic pancreatitis (CP) with T: 224 +/- 15 ngeq/mL (p less than 0.01) and in patients with pancreatic carcinoma (PCA) with T: 331 +/- 35 (p less than 0.001 vs controls, p less than 0.01 vs CP). Increased SRA was detected in patients with renal insufficiency (T: 2576 +/- 195 ngeq/mL, p less than 0.001). Diagnostic discrimination between AIP and ANP was achieved in 69% using T-SRA (sensitivity 31%, specificity 88%), and in 78% using P-SRA (sensitivity 54%, specificity 92%). Discrimination between CP and pancreatic carcinoma was possible in 68% (sensitivity 67%, specificity 71%). The diagnostic value of serum RNase is limited because of its low sensitivity, but increased T-SRA above a cutoff of 250 ngeq/mL and increased P-SRA above a cutoff of 620 ngeq/mL are specific for detecting pancreatic necrosis in the absence of renal impairment. The kidney is a major site for SRA clearance.
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PMID:Serum ribonuclease activity in the diagnosis of pancreatic disease. 203 16

Bovine seminal ribonuclease (BS-RNase), a dimeric homologue of RNase A, cleaves both single- and double-stranded RNA and inhibits the growth of tumor cells. Its catalytic activity against double-stranded RNA, either homopolymeric ([3H]polyA/polyU) or mixed sequence, is enhanced by bovine or human recombinant interferon-gamma (IFN-gamma). Activation is seen with as little as 4-10 interferon units per assay. Enhancing the degradation of double-stranded RNA, an intermediate in the growth cycle of many viruses, could contribute to IFN-gamma's ability to control cell growth and induce an antiviral state.
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PMID:Interferon-gamma activates the cleavage of double-stranded RNA by bovine seminal ribonuclease. 212 24

Unfolded ribonuclease (RNase) from porcine pancreas consists of a mixture of fast and slow-refolding species. The equilibrium distribution of these species differs strongly from other homologous RNases, because an additional proline residue is present at position 115 of the porcine protein. The major slow-folding species of porcine RNase contains incorrect proline isomers at Pro93 and at Pro114-Pro115. Both positions are presumably part of beta-turn structures in the native protein, as deduced from the structure of the homologous bovine RNase A. The folding kinetics of these molecules depend strongly on the conditions used. Under unfavorable conditions (near the unfolding transition), refolding is virtually blocked by the presence of the incorrect proline peptide bonds and partially folded intermediates with incorrect isomers could not be detected. As a consequence, folding is very slow under such conditions and the re-isomerization of Pro114-Pro115 is the first and rate-limiting step of folding. Under strongly native conditions (such as in the presence of ammonium sulfate), refolding is much faster. A largely folded intermediate accumulates with the turns around Pro93 and Pro114-Pro115 still in the non-native conformation. These results suggest that incorrect proline isomers strongly influence protein folding and that, under favorable conditions, the polypeptide chain can fold with two beta-turns locked into a non-native conformation. We conclude, therefore, that early formation of correct turn structure is not necessarily required for protein folding. However, the presence of incorrect turns, locked-in by non-native proline isomers, strongly decreases the rate of refolding. Alternative pathways of folding exist. The choice of pathway depends on the number and distribution of incorrect proline isomers and on the folding conditions.
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PMID:Role of two proline-containing turns in the folding of porcine ribonuclease. 231 96


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