Two tRNAIle1 species from an extreme thermophile, Thermus thermophilus HB8: effect of 2-thiolation of ribothymidine on the thermostability of tRNA.

N Horie, M Hara-Yokoyama, S Yokoyama, K Watanabe, Y Kuchino, S Nishimura, T Miyazawa

Index: Biochemistry 24(21) , 5711-5, (1985)

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Abstract

From Thermus thermophilus HB8 grown at 65 degrees C, two major tRNAIle species have been purified by column chromatography and polyacrylamide gel electrophoresis. The nucleotide sequence of one of these two tRNAIle1 species (tRNAIle1a) has been determined to be pGGGCGAUUAGCUCAGCUGmGUDAGAGCGCACGCCUGAUt6AAGCGUGAGm7GUCGGUGGs2T psi CAm1AGUCCACCAUCGCCCACCAOH. The nucleotide sequence of the other species (tRNAIle1b) is found to be the same as that of tRNAIle1a except for the modification in position 54; tRNAIle1a has s2T(54) while tRNAIle1b has T(54). The melting temperature of tRNAIle1a is as high as 86.2 degrees C while that of tRNAIle1b is 83.3 degrees C. The single replacement of an oxygen atom (2-carbonyl oxygen) of T(54) by a sulfur atom significantly contributes to the thermostability of the tRNAIle1a species. In addition, the methylation of G(18) and A(58) possibly contributes to the thermostability of T. thermophilus tRNAIle1a and tRNAIle1b species.