Abstract
To overcome the limitations imposed by the genetic code on the engineering of proteins with new or enhanced physical, chemical, or biological properties, we developed a general method for the site specific incorporation of unnatural amino acids into proteins directly in living cells.[1] An orthogonal tRNA/aminoacyl-tRNA synthetase pair (one that does not crossreact with host tRNAs and aminoacyl-tRNA synthetases) is evolved to deliver a specific non-natural amino acid into a protein in response to a nonsense or frameshift codon. To date, we have selectively incorporated over 40 unnatural amino acids into a diverse set of proteins in both prokaryotic and eukaryotic organisms using this methodology.[2]