2016-03-032016-03-0319960305-1048http://hdl.handle.net/11441/36772The variation in base composition at the three codon sites in relation to gene expressivity, the latter esti- mated by the Codon Adaptation Index, has been studied in a sample of 1371 Escherichia coli genes. Correlation and regression analyses show that in- creasing expression levels are accompanied by higher frequencies of base G at first, of base A at second and of base C at third codon positions. However, correla- tion between expressivity and base compositional biases at each codon site was only significant and positive at first codon position. The preference for G-starting codons as gene expression level increases is discussed in terms of translational optimizationapplication/pdfengAttribution-NonCommercial-NoDerivatives 4.0 Internacionalhttp://creativecommons.org/licenses/by-nc-nd/4.0/GuanosineBacterial geneCodon usageDna base compositionEscherichia coliGene expressionNonhumanPriority journalRegression analysisRna translationinfo:eu-repo/semantics/articleinfo:eu-repo/semantics/openAccesshttps://doi.org/10.1093/nar/24.13.2525