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

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