Patent ID: 8372960

Claim:
A mutant tRNA, which is a mutant of tRNA for tryptophan obtained from a microorganism selected from the group consisting of Mycoplasma capricolum, Bacillus halodouranns, Bacillus subtillis, Borrelia burgdorferi, Mycoplasma genitalium, Mycoplasma pneumoniae 1 , Mycoplasma pneumoniae 2 and Staphylococcus aureus N315, wherein the mutation consists of; (i) G at the 5′ end, (ii) C at 5th base from the 3′ end which pairs with the G of (i) at the 5′ end, and A at 4th base from the 3′ end which is adjacent to the 3′ side of the C of (ii), wherein the mutant tryptophan tRNA (mtRNAcuA CUA trp ) pairs with a UAG codon and has CUA as an anticodon; and where said mtRNA CUA trp has a higher efficiency of incorporation of an unnatural amino acid, a modified amino acid or a derivative thereof into a protein in an in-vitro cell-free translation system compared to the wild type tRNA trp or to a tRNA CUA trP that does not comprise the mutations of (i), (ii) or (iii).