An expanding genetic code

• Published in: Methods (San Diego, Calif.) Vol. 36; no. 3; pp. 227 - 238
• Main Authors: Xie, Jianming, Schultz, Peter G.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.07.2005
• Subjects: Amino Acids - chemistry; Amino Acids - genetics; Base Sequence; Directed evolution; Genetic Code; Molecular Sequence Data; Nucleic Acid Conformation; Orthogonal tRNA–synthetase pair; Protein Biosynthesis - genetics; Protein engineering; Protein Engineering - methods; Proteins - chemistry; RNA, Transfer - chemistry; RNA, Transfer - genetics; Unnatural amino acid incorporation; Protein engineering; Unnatural amino acid incorporation; Directed evolution; Orthogonal tRNA–synthetase pair
• ISSN: 1046-2023; 1095-9130
• DOI: 10.1016/j.ymeth.2005.04.010

A general method was recently developed that makes it possible to genetically encode unnatural amino acids (UAAs) with diverse physical, chemical or biological properties in Escherichia coli, yeast, and mammalian cells. Over 30 UAAs have been cotranslationally incorporated into proteins with high fidelity and efficiency by means of a unique codon and corresponding tRNA–synthetase pair. A key feature of this methodology is the orthogonality between the new translational components and their endogenous host counterparts. Specifically, the codon for the UAA should not encode a common amino acid; neither the new tRNA nor cognate aminoacyl tRNA synthetase should cross-react with any endogenous tRNA–synthetase pairs; and the new synthetase should recognize only the UAA and not any of the 20 common amino acids. This methodology provides a powerful tool for exploring protein structure and function both in vitro and in vivo, as well as generating proteins with new or enhanced properties.