Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.1.27.3 (RNase T1)
 1,228 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

Chemically synthesized yeast tRNA terminal fragments were reconstituted with natural tRNA fragments which were obtained by partial digestion with RNase T1. The synthetic 3'-nonanucleotide (I) accepted alanine (3% with respect to the intact tRNA) when combined with a 4-fold excess of the natural 5'-quarter and the chemically synthesized hexanucleotide (II) stimulated the aminoacylation of the natural 3'-half molecule.
 ...
PMID:Reconstitution of chemically synthesized ribooligonucleotides with naturally occurring tRNA fragments. 0 57

The nucleotide sequence of formylmethionine tRNA from an extreme thermophile, Thermus thermophilus HB8, was determined by a combination of classical methods using unlabeled samples to determine the sequences of the oligonucleotides of RNase T1 and RNase A digests and a rapid sequencing gel technique using 5'-32P labeled samples to determine overlapping sequences. Formylmethionine tRNA from T. thermophilus is composed of two species, tRNAf1Met and tRNAf2Met. Their nucleotide sequences are almost identical, and are also almost identical with that of E. coli tRNAfMet, except for slight modifications and replacements. Both species have modifications at three points which do not exist in E. coli tRNAfMet: 2'-O-methylation at G19, N-1-methylation at A59 and 2-thiolation at T55. Moreover U51 in E. coli tRNAfMet is replaced by C51 in both species, so that a G-C pair is formed between this C51 and G65. tRNAf2Met has a reversed G-C pair at positions 52 and 64 compared with those in tRNAf1Met and E. coli tRNAfMet. Other regions are mostly the same as those in all prokaryotic initiator tRNAs so far reported. The thermostability of these thermophile initiator tRNAs is discussed in relation to their unique modifications.
 ...
PMID:Nucleotide sequence of formylmethionine tRNA from an extreme thermophile, Thermus thermophilus HB8. 11 55

Dinucleoside diphosphates of the general type pGpN have been prepared enzymatically using ribonuclease N1. Alkylated uridines or cytidines, which are products of carcinogens acting on nucleic acids, were tested in dinucleoside diphosphates for their ability to stimulate the binding of Ala- or Val-tRNA to ribosomes. O2-Ethyl C and 3-methyl C functioned as U, but not as C. In contrast, 3-methyl U behaved as C, but not as U. Both O2 and O4-ethyl U could be recognized as C or U, although binding in both cases was weak. Thus, modifications of the hydrogen-bonding sites of U or C causes miscoding and could be considered to represent mutagenic reactions.
 ...
PMID:Synthesis and coding properties of dinucleoside diphosphates containing alky pyrimidines which are formed by the action of carcinogens on nucleic acids. 15 50

Antibodies specific for N6-methyladenosine (m6A) and for 7-methylguanosine (m7G) were immobilized on Sepharose and the resulting immunoadsorbents tested for their ability to retain specific oligonucleotides possessing the corresponding antigenic haptens (i.e. m6A and m7G). Results obtained with oligonucleotides derived from ribonuclease T1 digests of Escherichia coli tRNA (previously labeled with [methyl-3H]methionine) indicated that each immunoadsorbent quantitatively and exclusively retained those methyl-3H-labeled oligonucleotides possessing [methyl-3H]m6A and [methyl-3H]m7G. Elution and subsequent characterization of the retained methyl-3H-labeled oligonucleotides via DEAE-cellulose chromatography revealed the presence of several small oligonucleotides containing m7G and a single, larger oligonucleotide containing m6A. These findings are in accord with previously sequenced structures which indicate that numerous bacterial tRNA species possess m7G while only tRNAVal contains m6A.
 ...
PMID:Immunospecific retention of oligonucleotides possessing N6-methyladenosine and 7-methylguanosine. 32 62

Nucleotide sequences around kethoxal-reactive guanine residues of 23S RNA in 50S ribosomal subunits have been determined. By use of the diagonal paper electrophoresis method )Noller, H.F. (1974), Biochemistry 13, 4694-4703), 41 ribonuclease T1 oligonucleotides, originating from about 25 sites, were identified and sequenced. These sites are single stranded and accessible in free 50S subunits, and are thus potential sites for interaction with functional ligands during protein synthesis. Examination of these sequences for potential intermolecular base-pairing reveals the following: (1) There are 19 possible complementary combinations between exposed sequences in 16S and 23S RNA containing more than 4 base pairs: 15 containing 5 base pairs and 4 containing 6 base pairs. Nine of these complementary combinations contain 16S RNA sequences which we have previously shown to be protected from kethoxall by 50S subunits (Chapman, N.M., and Noller, H.F. (1977), J. Mol. Biol. 109, 131-149). (2) One of the exposed sites in 23S RNA has a sequence which is complementary to the invariant GT psi CR sequence in tRNA.
 ...
PMID:Nucleotide sequences of accessible regions of 23S RNA in 50S ribosomal subunits. 33 46

Two species of 32P-labelled leucine tRNA were highly purified from Candida (Torulopsis) utilis by successive column chromatographies. The purified major species of leucine tRNA 1 was completely digested with ribonuclease T1 [EC 3.1.4.8] and with pancreatic ribonuclease A [EC 3.1.4.22]. The resulting fragments were fractionated, and their nucleotide sequences were determined according to Barrell (1). The results of analyses of the two ribonuclease digests were consistent with each other, and indicated that this tRNA is composed of 85 nucleotide residues, including 14 modified nucleotides. A tentative total sequence has been derived on the basis of several features in the cloverleaf structure for tRNA.
 ...
PMID:Nucleotide sequence of leucine transfer RNA 1 from Candida (Torulopsis) utilis. 35 Aug 63

When treated at pH less than 4.5, yeast nuclei or chromatin lose endogenous RNA synthetic activity. This activity is regained by addition of exogenous RNA polymerases. The specificity of transcription in this system by homologous RNA polymerases I and III has been investigated by gel electrophoresis, hybridization analysis, and RNase T1 mapping. Exogenous RNA polymerase I selectively transcribes rRNA genes. The transcription of these genes by polymerase I is 30- and 8-fold more selective than RNA polymerase III and Escherichia coli polymerase holoenzyme, respectively. Exogenous RNA polymerase III synthesized RNAs similar in size to authentic 5 S RNA, 4.5 S pre-tRNA, and 4 S tRNA. Eleven per cent of this RNA is 5 S RNA as determined by hybridization. Neither polymerase I nor E. coli polymerase synthesizes detectable quantities of RNA in this size range. AT1 ribonuclease digestion of 5 S RNA synthesized by exogenous RNA polymerase III acting on acid-treated chromatin gives a fragment pattern corresponding to that of 5 S RNA. Thus, RNA polymerase III transcribes the entire 5 S gene in this system.
 ...
PMID:Specific gene transcription in yeast nuclei and chromatin by added homologous RNA polymerases I and II. 36 64

A second major species of leucine tRNA, tRNA Leu UAG (formerly designated tRNA Leu CUA) was purified from baker's yeast in a three-step procedure entailing BD-cellulose chromatography in the presence and absence of Mg2+ and Sephadex G-100 gel filtration. Results of aminoacylation and partial RNase T1 digestion experiments showed that this tRNA retains a native conformation under conditions that denature yeast tRNA Leu m5CAA (tRNA3 Leu). The primary structure of baker's yeast tRNA Leu UAG was elucidated by application of sensitive radioactive isotope derivative ("postlabeling") methods. Complete RNase T1 and A and partial RNase U2 fragments, prepared from non-radioactive tRNA and 5'-half and 3'-half molecules, were separated by two-dimensional polyethyleneimine-cellulose anion-exchange thin-layer chromatography and isolated by a novel micropreparative procedure affording high yields of these compounds in sufficient purity for subsequent tritium derivative analysis. Base composition and sequence of oligonucleotides were analyzed by tritium derivative methods. Molar ratios of the fragments were determined from the radioactivity of 3H-labeled nucleoside trialcohols in combination with base analysis. 2'-O-Methylated guanosine was characterized using the [gamma-32P]ATP/polynucleotide kinase reaction. The analysis of classical complete and partial RNase digests by the tritium derivative methods yielded the complete nucleotide sequence of the tRNA. A total of about 20 A260 units of the RNA was used for analysis, i.e. considerably less material than required for conventional spectrophotometric analysis. A different sequencing approach, consisting of a combination of "readout sequencing" with tritium sequencing of complete RNase T1 and A fragments, was applied to the 3'-half molecule. The 3'-half molecule was labeled with 32P at its 5' terminus, partially degraded with RNase T1, U2, and Phy1 and with alkali, and subjected to polyacrylamide gel electrophoresis. The sequence was read off the gel on the basis of cleavage patterns and size of the fragments. While the readout procedure provided only the positions of A, U, C, and G residues in the chain, additional information from tritium derivative analysis was utilized to define the positions of the modified nucleosides. The readout sequencing procedure was found to require less than 0.01 A260 unit of RNA and the analysis of the complete fragments about 6 A260 units. Interesting structural features of tRNA Leu UAG are (a) the location of unique, leucine tRNA iso-acceptor-specific sequences next to U-8, a constant nucleotide participating in synthetase recognition, (b) the occurrence of 1-methyladenosine in the T loop, a modification not present in the structurally related tRNA Leu m5CAA, and (c) the unusual presence of an unmodified uridine in the first position of the anticodon, which may be related to the unusual coding properties reported for this tRNA.
 ...
PMID:Yeast tRNA Leu UAG. Purification, properties and determination of the nucleotide sequence by radioactive derivative methods. 37 75

2-Thiocytidine 5'-triphosphate, s2CTP, is able to replace CTP as a substrate for tRNA nucleotidyltransferase. s2CMP can be incorporated into both cytidine sites of the C-C-A terminus common to all tRNAs, and in the absence of ATP into at least two additional positions. This was shown by alkylation of the 2-thiocytidine residues with iodo[14C]acetamide, total nucleoside analysis, microgel electrophoresis and analysis of RNase T1 fragments of these tRNAs. The incorporation of the 3'-terminal AMP is not influenced by the additional s2CMP residues at pH 9.0. However, at pH 7.6 the additional s2CMP residues are hydrolysed and AMP can be incorporated into the normal position. Two different tRNAs with terminal 2-thiocytidine alkylated by iodoacetamide inhibit tRNA nucleotidyltransferase. This inhibition is significantly slower if an elongated species is used compared to a tRNA with alkylated 2-thiocytidine in the normal position 75. The addition of 2-mercaptoethanol reactivates the enzyme and leads to a cytidine containing tRNA. This reaction identifies the attacking nucleophile of the enzyme as cysteine residue, which is probably identical to a cysteine residue found in a similar experiment reported previously. The mechanism of the enzymatic and chemical reactions is discussed.
 ...
PMID:Reversible inactivation of tRNA nucleotidyltransferase from baker's yeast by tRNAPhe containing iodoacetamide-alkylated 2-thiocytidine in normal and additional positions. 37 62


1 2 3 4 5 6 7 8 9 Next >>