Published on Oct. 14, 2011 in J Bioo Chem volume 286(41):35494-35498.

PubMed ID: 21873425

DOI: 10.1074/jbc.M111.279810

Abstract:

Variations in the genetic code are found frequently in mitochondrial decoding systems. Four non-universal genetic codes are employed in ascidian mitochondria: AUA for Met, UGA for Trp, and AGA/AGG(AGR) for Gly. To clarify the decoding mechanism for the non-universal genetic codes, we isolated and analyzed mitochondrial tRNAs for Trp, Met, and Gly from an ascidian, Halocynthia roretzi. Mass spectrometric analysis identified 5-taurinomethyluridine (τm5U) at the anticodon wobble positions of tRNAMet(AUR), tRNATrp(UGR), and tRNAGly(AGR), suggesting that τm5U plays a critical role in the accurate deciphering of all four non-universal codes by preventing the misreading of pyrimidine-ending near-cognate codons (NNY) in their respective family boxes. Acquisition of the wobble modification appears to be a prerequisite for the genetic code alteration.