Codon Optimization of mNeonGreen
We chose mneongreen, BBa_K1761003, as our part from the current registry to improve. We chose to improve this on the basis of codon optimisation, which states that organisms differ in the fraction of codons used for a particular amino acid. For example, there are some codons favoured by E.coli that are rare in yeast. This means that when expressing a recombinant protein, the sequence of this protein should vary according to the choice of chassis, in the hope that this will increase the translational efficiency .
We codon optimised this sequence for E.Coli, which resulted in the alteration of two bases that changed a rare codon to a more abundant codon. Most significantly, we changed the codon that codes for the leucine amino acid from TTG to the more abundant version, CTG. This improved codon is used for 50% of leucines, compared to the original TTG which only codes for 13% of leucine residues. In addition, there was a change to a more abundant valine codon. In the original mneongreen sequence, there was a TTG codon, which codes for 26% of valine residues in E.coli. In our improved sequence, we substituted this codon for the more abundant GTG, which codes for 37% of valine residues .