Patent ID: 7354761

Claim:
An isolated or cultured eukaryotic cell comprising an orthogonal tRNA synthetase (ORS) and an orthogonal tRNA (OtRNA), as a pair having the following provisios: (a.) said ORS preferentially aminoacylates said OtRNA, wherein preferential aminoacylation is defined in that said ORS aminoacylates endogenous tRNAs of the cell with a reduced efficiency as compared to endogenous tRNA synthetase aminoacylation of said endogenous tRNAs of the cell; (b.) said ORS preferentially aminoacylates said OtRNA with an unnatural amino acid, as compared to any natural amino acid; (c.) said OtRNA is aminoacylated by the endogenous tRNA synthetases of the cell with reduced efficiency as compared to aminoacylation of the endogenous tRNAs by said endogenous tRNA synthetases; and, (d.) said OtRNA recognizes a selector codon of an mRNA in said cell; and wherein k cat /K m for aminoacylation of the OtRNA by the ORS with the unnatural amino acid is higher than k cat /K m for aminoacylation of the OtRNA by the ORS with the natural amino acid.