US Patent 7566555 Method of expressing proteins comprising non-naturally-occurring amino acids

A method of expressing a protein having an unnatural amino acid integrated thereinto comprising expressing (A) a mutant tyrosyl tRNA synthase that is derived from Escherichia coli-origin tyrosyl tRNA synthase and has an elevated specificity for an unnatural tyrosine derivative compared with the specificity for tyrosine, (B) a suppressor tRNA originating in an eubacterium belonging to the genus Bacillus, Mycoplasma or Staphylococcus which is capable of binding to the above tyrosine derivative in the presence of the above mutant TyrRS, and (C) a desired protein gene having a nonsense mutation at a desired site in animal cells to thereby incorporate the above tyrosine derivative into the nonsense mutation site in the above protein.