Cupin Variants as a Macromolecular Ligand Library for Stereoselective Michael Addition of Nitroalkanes
Angew. Chem. 2020, 132, 7791-7794, 10.1002/ange.202000129
Cupin superfamily proteins (TM1459) work as a macromolecular ligand framework with a double-stranded β-barrel structure ligating to a Cu ion through histidine side chains. Variegating the first coordination sphere of TM1459 revealed that H52A and H54A/H58A mutants effectively catalyzed the diastereo- and enantioselective Michael addition reaction of nitroalkanes to an α,β-unsaturated ketone. Moreover, calculated substrate docking signified C106N and F104W single-point mutations, which inverted the diastereoselectivity of H52A and further improved the stereoselectivity of H54A/H58A, respectively.
Ligand type: Amino acidHost protein: Cupin superfamily protein (TM1459)Anchoring strategy: DativeOptimization: Chemical & geneticMax TON: 250ee: 99PDB: 6L2DNotes: ---
Modular Design of G-Quadruplex MetalloDNAzymes for Catalytic C–C Bond Formations with Switchable Enantioselectivity
J. Am. Chem. Soc. 2021, 143, 3555-3561, 10.1021/jacs.0c13251
Metal-binding DNA structures with catalytic function are receiving increasing interest. Although a number of metalloDNAzymes have been reported to be highly efficient, the exact coordination/position of their catalytic metal center is often unknown. Here, we present a new approach to rationally develop metalloDNAzymes for Lewis acid-catalyzed reactions such as enantioselective Michael additions. Our strategy relies on the predictable folding patterns of unimolecular DNA G-quadruplexes, combined with the concept of metal-mediated base-pairing. Transition-metal coordination environments were created in G-quadruplex loop regions, accessible by substrates. Therefore, protein-inspired imidazole ligandoside L was covalently incorporated into a series of G-rich DNA strands by solid-phase synthesis. Iterative rounds of DNA sequence design and catalytic assays allowed us to select tailored metalloDNAzymes giving high conversions and excellent enantioselectivities (≥99%). Based on their primary sequence, folding pattern, and metal coordination mode, valuable information on structure–activity relationships could be extracted. Variation of the number and position of ligand L within the sequence allowed us to control the formation of (S) and (R) enantiomeric reaction products, respectively.
Ligand type: DNA (G quadruplex)Host protein: metalloDNAzymeAnchoring strategy: Imidazole ligandosideOptimization: GeneticMax TON: ---ee: >99PDB: ---Notes: Km 35.2 uM, vmax-8.2 nM min-1
Synergistic Catalysis in an Artificial Enzyme by Simultaneous Action of Two Abiological Catalytic Sites
Nat. Catal. 2020, 3, 289-294, 10.1038/s41929-019-0420-6
Artificial enzymes, which are hybrids of proteins with abiological catalytic groups, have emerged as a powerful approach towards the creation of enzymes for new-to-nature reactions. Typically, only a single abiological catalytic moiety is incorporated. Here we introduce a design of an artificial enzyme that comprises two different abiological catalytic moieties and show that these can act synergistically to achieve high activity and enantioselectivity (up to >99% e.e.) in the catalysed Michael addition reaction. The design is based on the lactococcal multidrug resistance regulator as the protein scaffold and combines a genetically encoded unnatural p-aminophenylalanine residue (which activates an enal through iminium ion formation) and a supramolecularly bound Lewis acidic Cu(ii) complex (which activates the Michael donor by enolization and delivers it to one preferred prochiral face of the activated enal). This study demonstrates that synergistic combination of abiological catalytic groups is a robust way to achieve catalysis that is normally outside of the realm of artificial enzymes.
Ligand type: Amino acidHost protein: Lactoccal multidrug resistant regulator (LmrR)Anchoring strategy: Covalent; SupramolecularOptimization: GeneticMax TON: ---ee: >99PDB: ---Notes: 6:1 d.r