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Identification and characterization of tRNA (Gm18) methyltransferase from Thermus thermophilus HB8: domain structure and conserved amino acid sequence motifs
Author(s) -
Hori Hiroyuki,
Suzuki Tsutomu,
Sugawara Kazumasa,
Inoue Yorinao,
Shibata Takehiko,
Kuramitsu Seiki,
Yokoyama Shigeyuki,
Oshima Tairo,
Watanabe Kimitsuna
Publication year - 2002
Publication title -
genes to cells
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.912
H-Index - 115
eISSN - 1365-2443
pISSN - 1356-9597
DOI - 10.1046/j.1365-2443.2002.00520.x
Subject(s) - thermus thermophilus , biology , transfer rna , methyltransferase , thermus , methylation , biochemistry , peptide sequence , conserved sequence , amino acid , gene , genetics , enzyme , rna , thermophile , escherichia coli
Background: Transfer RNAs from an extreme thermophile, Thermus thermophilus , commonly possess 2′‐O‐methylguanosine at position 18 (Gm18) in the D‐loop. This modification is post‐transcriptionally introduced by tRNA (Gm18) methyltransferase . Results: Partial amino acid sequence data were obtained from purified T. thermophilus tRNA (Gm18) methyltransferase by peptide sequencing and mass spectrometry. The sequence data were used to screen the T. thermophilus genome database currently in progress, resulting in the identification of the corresponding gene. Purified recombinant enzyme showed a strict specificity for methylation at the 2′‐OH of G18 in tRNA. Sequence alignment with other known or putative methyltransferases elucidates that tRNA (Gm18) methyltransferases have specific conserved region as well as three consensus motifs found in RNA ribose 2′‐O‐methyltransferases. The enzyme truncated at its N and C termini by limited tryptic digestion still retained binding activity for S‐adenosyl‐ l ‐homocysteine, but lost the catalytic activity. Conclusion: This is the first report describing the identification of a methyltransferase gene of the trmH family through the analysis of a purified protein. Further, our results indicate that a restricted region(s) in the terminal amino acid residues of T. thermophilus tRNA (Gm18) methyltransferase are responsible for tRNA recognition and a main part of the enzyme is allocated for a catalytic core.