Hori H, Yamazaki N, Matsumoto T, Ueda T, Nishikawa K, Kumagai I, Watanabe K
Department of Biochemistry and Molecular Biology, Nippon Medical School, Tokyo, Japan.
Nucleic Acids Symp Ser. 1997(37):189-90.
Transfer RNA (guanosine-2'-)-methyltransferase (Gm-methylase, EC.2.1.1.32) from extreme thermophile, Thermus thermophilus HB27 is one of the tRNA-ribose modification enzymes; this enzyme specifically catalyze the transfer of a methyl group from S-adenosyl-L-methionine to 2'-OH of the ribose of the guanosine at position 18 in tRNA. A broad substrate specificity of Gm-methylase was observed using natural tRNAs as methyl group acceptors, which suggests that some local stractures common in tRNAs are recognized by the enzyme. By using yeast tRNA(Phe) variants obtained by transcription of their genes with T7 RNA polymerase, it was revealed that the residues G18 and G19, as well as the D-stem structure were primarily required for the methylation reaction and that the essentially minimal sequence for the substrate was Pyrimidine17-G18-G19. The other conserved sequences and the tertiary base-pairs were not essential, but G15, G46, U55 and C56 strongly affected the methylation efficiency.
嗜热栖热菌HB27的转移RNA（鸟苷-2'-）-甲基转移酶（Gm-甲基转移酶，EC.2.1.1.32）是tRNA核糖修饰酶之一；该酶特异性催化S-腺苷-L-甲硫氨酸的甲基转移至tRNA中第18位鸟苷核糖的2'-OH上。以天然tRNA作为甲基受体时，观察到Gm-甲基转移酶具有广泛的底物特异性，这表明tRNA中一些常见的局部结构可被该酶识别。通过使用用T7 RNA聚合酶转录其基因获得的酵母tRNA（Phe）变体，发现G18和G19残基以及D-茎结构是甲基化反应的主要必需条件，且底物的基本最小序列为嘧啶17-G18-G19。其他保守序列和三级碱基对并非必需，但G15、G46、U55和C56强烈影响甲基化效率。
