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Biochemistry. 2003 Jun 10;42(22):6735-46.

A new strategy for the site-specific modification of proteins in vivo.

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  • 1Department of Chemistry and Skaggs Institute for Chemical Biology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, California 92037, USA.


We recently developed a method for genetically incorporating unnatural amino acids site-specifically into proteins expressed in Escherichia coli in response to the amber nonsense codon. Here we describe the selection of an orthogonal tRNA-TyrRS pair that selectively and efficiently incorporates m-acetyl-l-phenylalanine into proteins in E. coli. We demonstrate that proteins containing m-acetyl-l-phenylalanine or p-acetyl-l-phenylalanine can be selectively labeled with hydrazide derivatives not only in vitro but also in living cells. The labeling reactions are selective and in general proceed with yields of >75%. In specific examples, m-acetyl-l-phenylalanine was substituted for Lys7 of the cytoplasmic protein Z domain, and for Arg200 of the outer membrane protein LamB, and the mutant proteins were selectively labeled with a series of fluorescent dyes. The genetic incorporation of a nonproteinogenic "ketone handle" into proteins provides a powerful tool for the introduction of biophysical probes for the structural and functional analysis of proteins in vitro or in vivo.

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