Extending Enzyme Molecular Recognition with an Expanded Amino Acid Alphabet
Extending enzyme molecular recognition with an expanded amino acid alphabet Claire L. Windlea,b, Katie J. Simmonsa,c, James R. Aulta,b, Chi H. Trinha,b, Adam Nelsona,c,1, Arwen R. Pearsona,2,3, and Alan Berrya,b,1 aAstbury Centre for Structural Molecular Biology, University of Leeds, Leeds LS2 9JT, United Kingdom; bSchool of Molecular and Cellular Biology, University of Leeds, Leeds LS2 9JT, United Kingdom; and cSchool of Chemistry, University of Leeds, Leeds LS2 9JT, United Kingdom Edited by Perry Allen Frey, University of Wisconsin–Madison, Madison, WI, and approved January 20, 2017 (received for review October 26, 2016) Natural enzymes are constructed from the 20 proteogenic amino for catalysis and arise through posttranslational modifications of acids, which may then require posttranslational modification or the the polypeptide chain (21, 22), allowing access to chemistries not recruitment of coenzymes or metal ions to achieve catalytic function. otherwise provided by the 20 proteogenic amino acids. Here, we demonstrate that expansion of the alphabet of amino acids Technologies for the protein engineer to incorporate Ncas into can also enable the properties of enzymes to be extended. A proteins at specifically chosen sites, either by genetic means (23–25) chemical mutagenesis strategy allowed a wide range of noncanon- or by chemical modification (26, 27), have recently been developed. ical amino acids to be systematically incorporated throughout an These approaches are powerful because, unlike traditional protein active site to alter enzymic substrate specificity. Specifically, 13 engineering with the 20 canonical amino acids, protein engineering different noncanonical side chains were incorporated at 12 different with Ncas has almost unlimited novel side-chain structures and positions within the active site of N-acetylneuraminic acid lyase chemistries from which to choose.
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