Patent ID: 8114627

Claim:
A method for producing in a translation system a protein comprising an unnatural amino acid at a selected position, the method comprising: (a) providing a translation system comprising: (i) a first unnatural amino acid that is sulfotyrosine; (ii) a first orthogonal aminoacyl-tRNA synthetase (O-RS) wherein the O-RS comprises an amino acid sequence that is a conservative variant of SEQ ID NO: 2, which conservative variant is at least 90% identical to SEQ ID NO: 2 and comprises a proline at a position corresponding to Leu65 and a lysine at a position corresponding to Leu162; (iii) a first orthogonal tRNA (O-tRNA), wherein said first O-RS preferentially aminoacylates said first O-tRNA with said sulfotyrosine and, (iv) a nucleic acid encoding said protein, wherein said nucleic acid comprises at least one selector codon that is recognized by said first O-tRNA; and, (b) incorporating said unnatural amino acid at said selected position in said protein during translation of said protein in response to said selector codon, thereby producing said protein comprising said unnatural amino acid at the selected position.