Abstract
The 20 amino acids, except for methionine and tryptophan, are coded for by 2 to 6 codons called synonymous codons. Synonymous codons are not used with equal frequency in protein coding sequences, and are used differently by different organisms. Although it has been thought that the codon usage is correlated with the translation efficiency, we found that translation efficiencies of synonymous codon groups are not always correlated with their usages in tobacco chloroplasts. This finding suggests that the inefficient codons in translation are selectively used in the several chloroplast mRNAs. Thus, we calculated the codon frequencies of individual chloroplast mRNAs, and found that tobacco rps16 mRNA contains many inefficient codons. Here, we analyzed the effect of inefficient codons in rps16 mRNA on its translation efficiency.
