Synonymous lysine codon usage modification in a mobile antibiotic resistance gene similarly alters protein production in bacterial species with divergent lysine codon usage biases because it removes a duplicate AAA lysine codon

The mobile antibiotic resistance gene bla IMP-1 is clinically important and has a synonymous AAA:AAG lysine codon usage bias of 73:27. This bias is like that seen in experimentally determined highly expressed genes in Escherichia coli and Acinetobacter baumanii , but quite different from that seen in Pseudomonas aeruginosa (26:74 AAA:AAG). Here we show that, paradoxically, shifting the AAA:AAG lysine codon bias to 8:92 in bla IMP-1 expressed from a natural promoter results in significantly more IMP-1 production in all three species. Sequential site directed mutagenesis revealed that increased IMP-1 production occurs following removal of an AAA,AAA double lysine codon and that otherwise, lysine codon usage had no observable impact on IMP-1 production. We conclude that ribosomal slippage at this poly-adenosine region reduces efficient translation of IMP-1 and that punctuating the region with guanine reduces ribosomal slippage and increases IMP-1 production.