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

---

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

Incubation of CMP in 2H2O with 0.5M cysteine methyl ester at p2H 5 and 37 degrees C for 24 h resulted in 43% exchange of 5-H to 5-2H. No deamination of the cytosine nucleus was noted during this treatment. Native and denatured DNA samples from calf thymus were treated in 3H2O with cysteine methyl ester at pH 5 and 37 degrees C for 24 h and incorporation of tritium into each DNA base was determined by enzymic digestion of the treated DNA. The order of the specific radioactivity found was cytosine greater than guanine greater than adenine greater than thymine for denatured DNA and guanine greater than adenine approximately cytosine greater than thymine for native DNA. The ratio of radioactivity for denatured/native was 11.6 for cytosine, 1.5 for guanine, 1.8 for adenine and 1.1 for thymine. Hence the incorporation in cytosine under the reaction conditions is preferential for single-stranded, nonhelical regions of DNA. Escherichia coli glutamic acid tRNA II was treated in 3H2O with 1.24 M cysteine methyl ester at pH 5 and 37 degrees C. The 24-h-treated tRNA was digested with ribonuclease T1 and the fragments were fractionated. Each fragment was then digested with ribonuclease T2 into mononucleotides and the radioactivity distribution among the bases was determined. The average radioactivity found for each of the bases of the four major nucleotides was cytosine greater than guanine approximately adenine greater than uracil. The radioactivity in cytosine varied greatly among the RNase T1 fragments, the ratio of the highest to the lowest radioactivity being 18.7. The corresponding value for guanine was 11.1, for adenine 4.73 and for uracil 3.64. Based on the data obtained, it was deduced that in this tRNA the anticodon loop, the dihydrouridine loop and the extra loop were "exposed" under the conditions employed for the labeling. The 5'-terminal cytosine of the anticodon loop was in a "non-exposed" state, a situation similar to that previously reported for E. coli tyrosine tRNA [Cashmore, A. R., Brown, D. M. & Smith, J. D. (1971) J. Mol. Biol. 59, 359-373] and for E. coli formylmethionine tRNA [Goddard J. P.+Schulman L. H. (1972) J. Biol. Chem. 247, 3864-3867]. Both cytosine 48, located at the 3'-terminal of the extra loop, and guanine 15 in the dihydrouridine loop were in an "emposed" state. This finding does not agree with a tRNA model in which this pair of cytosine and guanine, commonly found in tRNA sequences, forms hydrogen bondings. Positions 30--32, 61--64 and 71, which are located in the stems, were found to be strongly "buried".
...
PMID:Conformation of Escherichia coli glutamic acid tRNA II as studied by hydrogen-tritium exchange catalyzed by cysteine methyl ester. 0 69

In order to obtain information on the nature of the amino acid residues involved in the activity of ribonuclease U1 [EC 3.1.4.8], various chemical modifications of the enzyme were carried out. RNase U1 was inactivated by reaction with iodoacetate at pH 5.5 with concomitant incorporation of 1 carboxymethyl group per molecule of the enzyme. The residue specifically modified by iodoacetate was identified as one of the glutamic acid residues, as in the case of RNase T1. The enzyme was also inactivated extensively by reaction with iodoacetamide at pH 8.0 with the loss of about one residue each of histidine and lysine. When RNase U1 was treated with a large excess of phenylglyoxal, the enzymatic activity and binding ability toward 3'-GMP were lost, with simultaneous modification of about 1 residue of arginine. The reaction of citraconic anhydride with RNase U1 led to the loss of enzymatic activity and modification of about 1 residue of lysine. The inactivated enzyme, however, retained binding ability toward 3'-GMP. These results indicate that there are marked similarities in the active sites of RNases T1 and U1.
...
PMID:Chemical modifications of ribonuclease U1. 1 50

From a commercial digestive produced from Aspergillus saitoi, a ribonuclease [EC 3.1.4.23] having a molecular weight of 12,500 has been isolated in addition to the RNase reported previously, which had a molecular weight of 38,000. The enzyme was found to be homogeneous by chromatography on DEAE-cellulose, disc electrophoresis on polyacrylamide gel, and ultracentrifugation. The NH2-terminal amino acid was identified as glutamic acid. The amino acid composition indicated the presence of about 13 tyrosyl residues, 3 histidyl residues, and 2 half-cystine residues. The pH optimum of the RNase was 4.5, using RNA as a substrate. The enzyme was stable on heating at 70 degrees for 5 min from pH 2 to 10. It hydrolysed RNA completely to mononucleotides via 2', 3'-cyclic nucleotides. The rates of release of nucleotides and 2', 3'-cyclic nucleotides were in the order: guanylic acid is greater than adenylic acid is greater than cytidylic acid is greater than uridylic acid.
...
PMID:Purification and properties of a new ribonuclease from Aspergillus saitoi. 23 32

M protein was extracted from type 24, group A streptococci with pepsin at pH 5.8 and was further purified by ammonium sulfate precipitation, ribonuclease digestion, ion-exchange chromatography, and isoelectric focusing. The purified pepsin extract of M (pep M) protein was shown to be free of nontype-specific immunoreactivity in (a) complement fixation tests with heterologous M antiserum, (b) skin tests in normal adult guinea pigs, and (c) passive hemagglutination tests for the presence of lipoteichoic acid sensitizing or antigenic activity. The pep M24 was highly immunogenic; two of three rabbits developed opsonic antibody titers of 1:256 and the third a titer of 1:32 6 wk after a single injection of 100-pg doses of pep M24 emulsified in complete Freund's adjuvant. The antisera lacked nontype-specific antibodies and produced single precipitin lines in agar gel diffusion tests against crude HC1 extracts of the homologous M protein. Thus, the type-specific antigenic determinant(s) of type 24 M protein appears to be separable from immunotoxic, cross-reactive antigens without loss of immunogenicity in rabbits. The mobility of pep M24 upon electrophoresis in 10 percent sodium dodecyl sulfate pelyacrylamide gel was consistent with an average mol wt of 33,500 daltons. Amino acid analysis demonstrated a predominance of alanine, followed by glutamic acid, lysine, leucine, and aspartic acid. Pep M24 contained an estimated six to seven methionine residues and approximately ten phenylalanine residues per molecule. No other aromatic amino acids were detected. Automatic Edman degradation of pep M24 yielded the sequence of the first 29 amino acids (the amino terminal amino acid being valine) of the amino terminal region of the molecule. The detection of only one new amino acid at each step of Edman degradation confirmed the homogeneity of the purified pep M24.
...
PMID:Purification and properties of M protein extracted from group A streptococci with pepsin: covalent structure of the amino terminal region of type 24 M antigen. 32 68

(1) RNase Ms was inactivated by iodoacetate. The inactivation was most rapid at pH 6.0, and was inhibited in the presence of a denaturant such as 8 m urea or 6 m guanidine-HCL. (2) Competitive inhibitors protected RNase Ms from inactivation by iodoacetate; the effect was in the order 2',(3')-GTP greater than 2',(3')-AMP, 2',(3')-UMP greater than or equal to 2',(3')-CMP. The order is not consistent with that of the binding constants of the 4 nucleotides towards RNase Ms (A is greater than C greater than G greater than U). (3) RNase Ms was inactivated with the concomitant incorporation of one molar equivalent of carboxymethly group. The following evidence indicated that the carboxymethyl group was incorporated into the carboxyl group of an aspartic acid or glutamic acid residue. (i) The carboxymethyl group incorporated into RNase Ms was liberated by treatment with 0.1 n NaOH or 1 m hydroxylamine. (ii) The amino acid composition of carboxymethylated RNase Ms (CM RNase Ms) after acid hydrolysis is similar to that of RNase Ms. (4) 14C-Labeled CM RNase Ms was digested successively with alkaline protease and amino-peptidase M. The radioactive amino acid released was eluted just before aspartate on an amino acid analyzer. After hydrolysis with 6 n HCL, glutamic acid was produced exclusively from the radioactive amino acid. The specific radioactivity of this amino acid calculated from the radioactivity and glutamic acid formed was practctically the same as that of CM RNase Ms. Thus, it was concluded that a carboxymethyl group was incorporated at the carboxyl group of a glutamic acid residue of RNnase Ms. (5) CM RNase Ms bound with 2'-AMP to the same extent as native RNase Ms, but bound to a lesser extent with 2',(3')-GMP. (6) Although the conformation of CM RNase Ms as judged from the CD spectrum was practically the same as that of native RNase Ms, the reactivity of CM RNase Ms towards dinitrofluorobenzene was different from that of native RNase Ms, indicating some difference in the conformation. (7) These results indicate that one glutamic acid residue is involved in the active of RNase Ms.
...
PMID:Carboxymethylation of a minor ribonuclease from Aspergillus saitoi. 47 29

During the first 10 days after peripheral deafferentation of the mouse olfactory bulb stereoselective binding of L-[3H]carnosine declines markedly. The initial phase of this decline is due to a decrease in binding site stereoselectivity, which is then followed by a loss of assayable binding sites. The specificity of inhibition of L-[3H]carnosine binding by various peptides is also altered after denervation. Competitive inhibitors of carnosine binding become less potent after denervation, while analogues which are not competitive inhibitors remain equipotent before and after denervation. Several carnosine analogues that are normally poor inhibitors become more potent after denervation. Treatment of bulb membranes with trypsin, RNase and hyaluronidase, but not DNase or collagenase, resulted in significant alterations in carnosine binding. L-, but not D-carnosine, protected the binding site from trypsin digestion, and induced additional binding in bulb membranes in a dose-and temperature-dependent fashion. Preincubation of membranes with L-carnosine also led to the induction of additional carnosine binding in membranes from cerebral cortex, cerebellum and deafferentated bulbs but not from muscle. Bulbs from newborn mice contain about one-half of the adult levels of binding and no significant sex differences in carnosine binding were detected in bulbs from adult rats. L-[3H]carnosine binding was two-fold higher in the anterior compared to the posterior portion of the bulb, but there were no significant differences in binding of opiate, GABA, alpha-adrenergic, muscarinic cholinergic, benzodiazepine of glutamic acid receptor ligands.
...
PMID:L-[3H]Carnosine binding in the olfactory bulb. II. Biochemical and biological studies. 48 25

Conjugates of two unlike proteins can be prepared via the intermolecular disulfide interchange reaction, namely, protein A containing thiol groups reacts with protein B containing 4-dithiopyridyl groups to yield a conjugate with the release of 4-thiopyridone. Thiol groups can be introduced into proteins upon amidination with methyl 3-mercaptopropionimidate ester or 2-iminothiolane, and 4-dithiopyridyl groups can be introduced into proteins with these same reagents in the presence of 4,4'-dithiodipyridine. 2-Iminothiolane is stable on storage in contrast to the known lability of imidate esters; therefore 2-iminothiolane is a more convenient reagent for the modification of protein than are the imidate esters. All the reactions can be carried out easily under mild conditions in good yields. Conjugates of bovine plasma albumin with itself, ribonuclease, or a copolymer of D-glutamic acid and D-lysine and of sheep antibody and horseradish peroxidase were prepared with modified proteins containing an average of 1 to 5 thiol or dithiopyridyl groups per mol. These conjugates formed mainly dimers, trimers, and tetramers. The peroxidase labeled antibody retained more than 80% of its enzymatic and antigenic binding activities.
...
PMID:Preparation of protein conjugates via intermolecular disulfide bond formation. 64 98

Apoferritin particles were found in mouse peritoneal macrophages cultured in vitro. They were found as 20S particles in the "ribosomal fraction" of macrophages labeled with L-[14C]glutamic acid. Possibilities that they were breakdown products of ribosomes or of other well-known contaminants of the ribosomal fraction were excluded because they did not incorporate [5-3H]uridine. They were resistant to RNase and were relatively resistant to detergent. The antibody against horse spleen apoferritin precipitated about 70% of the particles in the 20S region, judging by measurement of radioactivity. On in vitro incubation with Fe2+ and suitable oxidizing agents the sedimentation coefficient of 80% of the 20S particles changed to about 60S, which corresponds to that of ferritin. SDS-polyacrylamide gel electrophoresis revealed the presence of subunit structures with the same molecular size as that of mouse liver apoferritin. Under the electron microscope, the particles appeared spherical with a relatively uniform diameter of about 130 A.
...
PMID:Synthesis of apoferritin in mouse peritoneal macrophages. Characterization of 20 S particles. 82 42

The membrane penicillinase of Bacillus licheniformis 749/C differs from the exopenicillinase in that it has an additional 24 amino acid residues and a phosphatidylserine at the NH2 terminus (Yamamoto, S., and Lampen, J.O. (1976) J. Biol. Chem. 251, 4095-4101). The conversion of the membrane penicillinase to the exo form is probably carried out by a specific penicillinase-releasing protease (PR-protease) whose properties are generally consistent with the properties of penicillinase secretion. The substrate specificity of the PR-protease was determined by identifying the NH2 and COOH termini of the peptides produced by hydrolysis of ribonuclease B and beef insulin. The enzyme hydrolyzed only peptide bonds involving the carboxyl groups of serine or thrombine. Similar bonds in synthetic di- or tripeptides of L-serine were not cleaved. The existence of seryl-lysine and threonyl-glucamic acid bonds in the protease-susceptible (phospholipopeptide) region of the membrane penicillinase and the presence of only lysine or glutamic acid at the NH2 terminus of the exoenzyme released in vivo are consistent with the specificity of PR-protease; hence, we propose that this enzyme has an essential role in the formation of exopenicillinase. The PR-protease is a potential tool for protein sequence determination because of its narrow and novel substrate specificity.
...
PMID:Penicillinase-releasing protease of Bacillus licheniformis 749 Specificity for hydroxyamino acids. 83 38

Urine contains nondialyzable inhibitors of calcium oxalate crystal growth. We have pursued the hypothesis that these inhibitors may, in part, be acidic peptides and polyribonucleotide fragments. Homopolyribonucleotides and RNA inhibit calcium oxalate crystal growth at 5 x 10(-6) M of constituent ribonucleotide, whereas the monomer nucleotides are inactive at 10(-4) M. Poly-L-aspartic or glutamic acid are also inhibitory at 5 X 10(-6) M of amino acid, whereas the monomeric amino acids are inert. Gastric pepsin, a naturally occurring acidic peptide, is inhibitory. Incubation with nonspecific protease reduced the inhibitory effectiveness of normal human urine consistently and significantly, a fact compatible with an important contribution of peptides. A variable additional reduction was produced by subsequent treatment with ribonuclease, suggesting only a small role for polyribonucleotide. Sequential ion exchange and gel filtration chromatography and preparative disc gel electrophoresis yielded inhibitory material enriched with peptides that were strongly acidic and high in proline. Peptides and ribonucleotides seem to contribute to urinary nondialyzable crystal growth inhibitory activity.
...
PMID:Acidic peptide and polyribonucleotide crystal growth inhibitors in human urine. 92 Aug 14


1 2 3 4 5 Next >>

---