Publication Details (including relevant citation information):
Yuksel, D.; Pamuk, D.; Ivanova, Y.; Kumar, K. "Protein Engineering Using Noncanonical Amino Acids" in Protein Engineering and Design Park, S. and Cochran, J. Eds., Taylor & Francis 2009, invited chapter, pp 205-222.
The limited set of structural and chemical functionalities represented in the side
chains of the canonical amino acids necessitate post-translational processing of
expressed protein products. Such processing combinatorially expands both the diversity
and functional attributes of proteins. This suggests that while the extant set of
twenty encoded amino acids can support the rudimentary functions of living systems,
optimized function requires a larger set. Site directed mutagenesis has proven to be
an invaluable tool in tailoring structural features of enzymes and has allowed detailed scrutiny of function and creation of enzymatic activities not found in nature. Nevertheless, the limited set of functional groups available constrains the range of possible applications. One could envision entirely new functions for proteins, or even the evolution of entire organisms endowed with extrabiological properties, if the set of functional groups present on the side chains can be expanded.
Schultz and Chamberlin pioneered the incorporation of unnatural amino acids
using nonsense codon suppression. More than 150 unnatural amino acids have been incorporated by this technique both in vitro and in vivo, allowing interrogation of mechanism and structure in unsurpassed detail. This chapter focuses on applications made possible by introducing unnatural amino acids into proteins with a brief overview of methodologies of incorporation.
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