Patent ID: 8735093

Claim:
A mutant pyrrolysyl-tRNA synthetase comprising substitution of at least one amino acid residue selected from tyrosine at position 306, leucine at position 309, and cysteine at position 348, which constitute a pyrrolysine-binding site, and tyrosine at position 384, in the amino acid sequence of the pyrrolysyl-tRNA synthetase set forth in SEQ ID NO:2, wherein said substitution of the amino acid residue comprises: substitution of alanine for tyrosine at position 306, substitution of phenylalanine for tyrosine at position 384, double substitution in which alanine is substituted for tyrosine at position 306 and phenylalanine is substituted for tyrosine at position 384, or double substitution in which alanine is substituted for leucine at position 309 and valine is substituted for cysteine at position 348, wherein said mutant pyrrolysyl-tRNA synthetase aminoacylates a pyrrolysine tRNA with N ε -benzyloxycarbonyl-lysine more efficiently than the wild type pyrrolysyl-tRNA synthetase having the amino acid sequence set forth in SEQ ID NO: 2.