Codon reading patterns in Saccharomyces cerevisiae mitochondria based on sequences of mitochondrial tRNAs

Abstract

The sequences of Saccharomyces cerevisiae mitochondrial tRNA 1 Arg, tRNA 2 Arg, tRNA Gly, tRNA 2 Lys tRNA Leu and tRNA Pro are reported. Special structural features were found in tRNA Pro, which has A 8, C 21, A 48 instead of the constant residues U 8, A 21 and pyrimidine 48, and in tRNA 2 Lys, which has a U excluded from basepairing and bulging out from the TΨC stem. The tRNA 1 Arg, tRNA 2 Lys and tRNA Leu, which belong to two-codon families ending in a purine, have a modified uridine in the wobble position, which prevents misreading of C and U. It is likely to be 5-carboxymethylaminomethyluridine. tRNA Gly and tRNA Pro have an unmodified uridine in the wobble position allowing the reading of all four codons of a four-codon family. However, tRNA 2 Arg, which is a minor species and belongs to the CGN four-codon family, has an unmodified A in the wobble position. This very unusual feature raises the problem of the mechanism by which the codons CGA, CGG and CGC are recognized.