5-[[(Carboxymethyl)amino]methyl]uridine is found in the anticodon of yeast mitochondrial tRNAs recognizing two-codon families ending in a purine

The modified nucleoside (U*) present in the wobble position of Saccharomyces cerevisiae mitochondrial tRNA(Leu) and tRNA(Trp) was isolated by thin-layer chromatography and HPLC. Its chromatographic, UV spectral, and mass spectrometric properties were shown to be identical with those of 5- [[(carboxymethyl)amino]methyl]uridine (cmnm5U). This nucleoside found in yeast mitochondrial tRNAs reading two-codon families ending in a purine permits the selective recognition of A and G in the third codon position.