Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.1.27.3 (RNase T1)
 1,228 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Recognition sites of tRNA by tRNA(guanosine-2'-)-methyltransferase (Gm-methylase) [EC 2.1.1.34] from an extreme thermophile, Thermus thermophilus HB27, were studied by two independent methods--fragment reactions and footprinting analyses, using yeast tRNA(Phe) and Escherichia coli tRNA(fMet) as substrates. None of the tRNA-derived oligonucleotides which have the G-G sequence but are not long enough to form the "stem-loop" structure could be methylated by Gm-methylase. The 5'-half fragments having the intact D-"stem-loop" structure served as substrates for Gm-methylase, with a similar Vmax but 6-8 times larger Km, as compared with the intact tRNAs. The results of footprinting analyses were consistent with the foregoing findings. Gm-methylase protected only the D-loop region of tRNA from RNase T1 attack, but other parts of tRNA extending from the amino acid stem to the T arm became more sensitive to RNase T1, suggesting a considerable change of tRNA tertiary structure due to complex formation with Gm-methylase. These results indicate that a D-"stem-loop" structure is a prerequisite for recognition by Gm-methylase.
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PMID:Recognition sites of tRNA by a thermostable tRNA(guanosine-2'-)-methyltransferase from Thermus thermophilus HB27. 218 56

Previously we have isolated the specific RNA methyltransferase from the nucleoli of Ehrlich ascites tumor cells. The purified enzyme was found to be specific for methylation of C5 position of cytosine residue in ribosomal RNA in vitro (Obara, 1982b). In the present study, we have investigated the recognition mechanisms of RNA structure by this enzyme from the points of view of both primary and secondary structures. Analysis of in vitro methylation product by ribonuclease T1 digestion indicated the methylation-site(s) was limited to a certain number of nonanucleotide. The next experiments with either Sl nuclease or actinomycin D and ethidium bromide suggested that the enzyme modified only cytidine residue in or located close to the double stranded part of RNA. On the other hand, the characterization of analogues of cytidine residue in the RNA at molecular level showed that the methylation of rRNA was inhibited by either cytidine, CDP or CTP, but little inhibition was observed in the presence of cytosine, 5-methylcytidine and CMP.
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PMID:Recognition of the ribosomal RNA structures by purified nucleolar RNA methyltransferase. 667 41

An S-adenosylmethionine-=dependent tRNA (guanosine-2'-)-methyltransferase (EC 2.1.1.34) was purified to the homogeneous state (2,400-fold) from a cell-free extract of an extreme thermophile, Thermus thermophilus HB27. The enzyme was highly resistant to heat as reported for other enzymes from thermophilic organism. The enzyme is monomeric and its molecular weight was estimated to be about 20,000. The Km values for S-adenosylmethionine and for Escherichia coli tRNAPhe were determined to be 0.47 microM and 10 nM, respectively, while the Ki for a competitive inhibitor S-adenosylhomocysteine, was 1.67 microM. When yeast tRNAPhe was methylated with the purified Gm-methyltransferase, a stoichiometric amount of methyl group was incorporated into the invariant guanosine at position 18 in the D-loop. Yeast tRNAPhe and E. coli tRNAMet, which were quantitatively methylated with the enzyme, were very similar to the native tRNAs with regard to amino acid acceptor activity and melting temperature, but were more resistant to RNase T1 and RNase A digestions than the corresponding native tRNAs.
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PMID:A thermostable tRNA (guanosine-2')-methyltransferase from Thermus thermophilus HB27 and the effect of ribose methylation on the conformational stability of tRNA. 708 32

The fmu gene product has been proposed to be an RNA methyltransferase [Koonin, E. V. (1994) Nucleic Acids Res. 22, 2476-2478]. Fmu has been cloned and expressed, and the encoded 47 kDa protein has been purified and characterized. The enzyme catalyzed specific methylation of C967 of unmodified 16S rRNA transcripts. A 16mer stem-loop structure containing C967 (nt 960-975) was also a good substrate for the enzyme in vitro. Methylation of C967 was confirmed by several methods including analysis of RNase T1 digests and nearest-neighbor analysis. Fmu did not catalyze methylation of transcripts of 23S rRNA. E. coli cells that contained kanr-disrupted fmu produced 16S rRNA that could be specifically methylated by Fmu in vitro at C967 but not C1407. Further, fmu disruption did not significantly alter the growth rate of E. coli in rich or minimal media. We propose renaming this ORF "rrmB" and the enzyme "RrmB" for rRNA methyltransferase.
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PMID:Identification of the 16S rRNA m5C967 methyltransferase from Escherichia coli. 1019 18