Lewis, J.C.

ChemBioChem 2014, 15, 223-227, 10.1002/cbic.201300661

Strain‐promoted azide–alkyne cycloaddition (SPAAC) can be used to generate artificial metalloenzymes (ArMs) from scaffold proteins containing a p‐azido‐L‐phenylalanine (Az) residue and catalytically active bicyclononyne‐substituted metal complexes. The high efficiency of this reaction allows rapid ArM formation when using Az residues within the scaffold protein in the presence of cysteine residues or various reactive components of cellular lysate. In general, cofactor‐based ArM formation allows the use of any desired metal complex to build unique inorganic protein materials. SPAAC covalent linkage further decouples the native function of the scaffold from the installation process because it is not affected by native amino acid residues; as long as an Az residue can be incorporated, an ArM can be generated. We have demonstrated the scope of this method with respect to both the scaffold and cofactor components and established that the dirhodium ArMs generated can catalyze the decomposition of diazo compounds and both SiH and olefin insertion reactions involving these carbene precursors.

Lewis, J.C.

Nat. Commun. 2015, 6, 10.1038/ncomms8789

Artificial metalloenzymes (ArMs) formed by incorporating synthetic metal catalysts into protein scaffolds have the potential to impart to chemical reactions selectivity that would be difficult to achieve using metal catalysts alone. In this work, we covalently link an alkyne-substituted dirhodium catalyst to a prolyl oligopeptidase containing a genetically encoded L-4-azidophenylalanine residue to create an ArM that catalyses olefin cyclopropanation. Scaffold mutagenesis is then used to improve the enantioselectivity of this reaction, and cyclopropanation of a range of styrenes and donor–acceptor carbene precursors were accepted. The ArM reduces the formation of byproducts, including those resulting from the reaction of dirhodium–carbene intermediates with water. This shows that an ArM can improve the substrate specificity of a catalyst and, for the first time, the water tolerance of a metal-catalysed reaction. Given the diversity of reactions catalysed by dirhodium complexes, we anticipate that dirhodium ArMs will provide many unique opportunities for selective catalysis.

Chen, Y.; Wang, C.

Angew. Chem. Int. Ed. 2020, 59, 3444-3449, 10.1002/anie.201912962

The diverse secondary structures of nucleic acids are emerging as attractive chiral scaffolds to construct artificial metalloenzymes (ArMs) for enantioselective catalysis. DNA‐based ArMs containing duplex and G‐quadruplex scaffolds have been widely investigated, yet RNA‐based ArMs are scarce. Here we report that a cyclic dinucleotide of c‐di‐AMP and Cu2+ ions assemble into an artificial metalloribozyme (c‐di‐AMP⋅Cu2+) that enables catalysis of enantioselective Friedel–Crafts reactions in aqueous media with high reactivity and excellent enantioselectivity of up to 97 % ee. The assembly of c‐di‐AMP⋅Cu2+ gives rise to a 20‐fold rate acceleration compared to Cu2+ ions. Based on various biophysical techniques and density function theory (DFT) calculations, a fine coordination structure of c‐di‐AMP⋅Cu2+ metalloribozyme is suggested in which two c‐di‐AMP form a dimer scaffold and the Cu2+ ion is located in the center of an adenine‐adenine plane through binding to two N7 nitrogen atoms and one phosphate oxygen atom.