Abstract
The 20 amino acids, except for methionine and tryptophan, are codoed 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. It has been thought that the codon usage is correlated with the translation efficiency. Using an in vitro translation system from tobacco chloroplasts, we devised an in vitro assay for relative translation rates of synonymous codons. We found that translation efficiencies of synonymous codons are not always correlated with codon usage in tobacco chloroplasts. Here, we analyzed the effect of selection of synonymous codons on the translation efficiency of protein coding region from several tobacco chloroplast mRNAs.
