Codon recognition rules in yeast mitochondria.

Abstract

The mitochondrial genome of S. cerevisiae codes for 24 tRNA. The nucleotide sequences of the tRNA genes suggest a unique set of rules that govern the decoding of the mitochondrial genetic code. The 4 codons of unmixed families are recognized by single tRNA that always have a U in the wobble position of the anticodon. The codons of the mixed families are read by 2 different tRNA. Codons terminating in a C or U are recognized by tRNA with a G and codons terminating in a G or A are recognized by tRNA with a U in the corresponding positions of the anticodons. There are 2 exceptions to these rules. In the AUN family for isoleucine and methionine, the isoleucine tRNA has a G and the methionine tRNA has a C in the wobble position. The tRNA for the arginine CGN family also has an A in the wobble position of the anticodon. The CGN codons have not been found in the mitochondrial genes sequences to date. The simplified decoding system of yeast mitochondria allows all the codons to be recognized by only 24 tRNA.