A team of investigators at The Scripps Research Institute and its Skaggs Institute for Chemical Biology in La Jolla, California has modified a form of the bacterium Escherichia coli to use a 22-amino acid genetic code. “We have demonstrated the simultaneous incorporation of two unnatural amino acids into the same polypeptide,” says Professor Peter G. Schultz, Ph.D., who holds the Scripps Family Chair in Chemistry at Scripps Research. “Now that we know the genetic code is amenable to expansion to 22 amino acids, the next question is, how far can we take it?” In an upcoming issue of the journal Proceedings of the National Academy of Sciences, the team describes how they engineered this modified form of E. coli to make myoglobin proteins with 22 amino acids—incorporating the unnatural amino acids O-methyl-L-tyrosine and L-homoglutamine in addition to the naturally occurring 20.
