SYNONYMOUS CODON BIAS IS RELATED TO GENE LENGTH IN ESCHERICHIA-COLI -SELECTION FOR TRANSLATIONAL ACCURACY

The level of synonymous codon bias is shown to be positively correlate d to gene length in Escherichia coli genes which are thought to be exp ressed at similar levels; these are genes whose products are present i n multimeric proteins in equimolar amounts. It is argued that the posi tive correlation could be caused by selection to avoid missense errors during translation. Since the cost of producing a protein is proporti onal to its length, selection in favor of codons which increase accura cy should be greater in longer genes, and long genes should therefore have higher synonymous codon bias. It is also shown that there is vari ation in synonymous codon use which is independent of either expressio n level, gene length, amino acid composition, or chromosomal location. This variation is consistent with selection for translational accurac y but may have other origins.