Major tyrosine identity determinants in Methanococcus jannaschii and Saccharomyces cerevisiae tRNA(Tyr) conserved but expressed differently

Using in vitro, tRNA transcripts and minihelices it was shown that the tyro sine identity for tRNA charging by tyrosyl-tRNA synthetase (TyrRS) from the archaeon Methanococcus jannaschii is determined by six nucleotides: the di scriminator base A73 and the first base-pair C1-G72 in the acceptor stem to gether with the anticodon triplet. The anticodon residues however, particip ate only weakly in identity determination, especially residues 35 and 36, T he completeness of the aforementioned identity set was verified by its tran fer into several tRNAs which then become as efficiently tyrosylatable as th e wild-type transcript from M. jannaschii, Temperature dependence experimen ts on both the structure and the tyrosylation properties of M. jannaschii a nd yeast tRNA(Tyr) transcripts show that the archaeal transcript has greate r structural stability and enhanced aminoacylation behaviour than the yeast transcript. Tyrosine identity in M. jannaschii is compared to that in yeas t, and the conservation of the major determinant in both organisms, namely the C1-G72 pair, gives additional support to the existence of a functional connection between archaeal and eukaryotic aminoacylation systems.