Mutation and selection on the anticodon of tRNA genes in vertebrate mitochondrial genomes

摘要: The H-strand of vertebrate mitochondrial DNA is left single-stranded for hours during the slow replication. This facilitates C-->U mutations on (and consequently G-->A L-strand) via spontaneous deamination which occurs much more frequently than double-stranded DNA. For 12 coding sequences (CDS) collinear with L-strand, NNY synonymous codon families (where N stands any four nucleotides and Y either C or U) end mostly C, NNR NNN R A G) A. lone ND6 gene other strand, bias opposite, ending U G. These patterns are consistent strand-specific mutation bias. usage biased towards C-ending A-ending in CDS affects codon-anticodon adaptation. wobble site anticodon always G dominated by codons codons. only, but consistent, exception tRNA-Met consistently has a 5'-CAU-3' base-pairing AUG (the translation initiation codon) instead frequent AUA. observed CAU (matching AUG) would increase rate reduce peptide elongation because most methionine AUA, whereas unobserved UAU AUA) at cost rate. suggests importance maximizing initiation.