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Expanding the Scope of Single- and Double-Noncanonical Amino Acid Mutagenesis in Mammalian Cells Using Orthogonal Polyspecific Leucyl-tRNA Synthetases

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journal contribution
posted on 06.11.2017, 00:00 by Yunan Zheng, Raja Mukherjee, Melissa A. Chin, Peter Igo, Martin J. Gilgenast, Abhishek Chatterjee
Engineered aminoacyl-tRNA synthetase/tRNA pairs that enable site-specific incorporation of noncanonical amino acids (ncAAs) into proteins in living cells have emerged as powerful tools in chemical biology. The Escherichia coli-derived leucyl-tRNA synthetase (EcLeuRS)/tRNA pair is a promising candidate for ncAA mutagenesis in mammalian cells, but it has been engineered to charge only a limited set of ncAAs so far. Here we show that two highly polyspecific EcLeuRS mutants can efficiently charge a large array of useful ncAAs into proteins expressed in mammalian cells, while discriminating against the 20 canonical amino acids. When combined with an opal-suppressing pyrrolysyl pair, these EcLeuRS variants further enabled site-specific incorporation of different combinations of two distinct ncAAs into proteins expressed in mammalian cells.