Recognition sites of bovine mitochondrial serine tRNA specific for codons AGY [tRNASer(AGY)] by the cognate mitochondrial seryl-tRNA synthetase were studied using a range of tRNASer(AGY) variants which were obtained by the in vitro transcription of synthetic tRNA genes with T7 RNA polymerase. Base replacements in the anticodon and discriminator sites did not affect serine acceptance. However, deletion and/or replacement in the T-loop region completely deprived the variants of their charging activities. Point mutation experiments in this region also showed that the adenosine residue in the middle of the T-loop (position 58), which is involved in tertiary interaction between the T-loop and the truncated D-arm [de Bruijn and Klug, 1983] played a significant role in the recognition process by the synthetase.
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