A Rhodium Complex-Linked β-Barrel Protein as a Hybrid Biocatalyst for Phenylacetylene Polymerization
Chem. Commun. 2012, 48, 9756, 10.1039/C2CC35165J
Our group recently prepared a hybrid catalyst containing a rhodium complex, Rh(Cp)(cod), with a maleimide moiety at the peripheral position of the Cp ligand. This compound was then inserted into a β-barrel protein scaffold of a mutant of aponitrobindin (Q96C) via a covalent linkage. The hybrid protein is found to act as a polymerization catalyst and preferentially yields trans-poly(phenylacetylene) (PPA), although the rhodium complex without the protein scaffold normally produces cis PPA.
Host protein: Nitrobindin (Nb)Optimization: ---Max TON: ---ee: ---PDB: ---Notes: ---
Asymmetric Hydrogenation with Antibody-Achiral Rhodium Complex
Org. Biomol. Chem. 2006, 4, 3571, 10.1039/B609242J
Monoclonal antibodies have been elicited against an achiral rhodium complex and this complex was used in the presence of a resultant antibody, 1G8, for the catalytic hydrogenation of 2-acetamidoacrylic acid to produce N-acetyl-L-alanine in high (>98%) enantiomeric excess.
Host protein: Antibody 1G8Anchoring strategy: AntibodyOptimization: ---Max TON: ---ee: ---PDB: ---Notes: ---
A Whole Cell E. coli Display Platform for Artificial Metalloenzymes: Poly(phenylacetylene) Production with a Rhodium–Nitrobindin Metalloprotein
ACS Catal. 2018, 8, 2611-2614, 10.1021/acscatal.7b04369
Whole cell catalysis is, in many cases, a prerequisite for the cost-effective production of chemicals by biotechnological means. Synthetic metal catalysts for bioorthogonal reactions can be inactivated within cells due to abundant thiol derivatives. Here, a cell surface display-based whole cell biohybrid catalyst system (termed ArMt bugs) is reported as a generally applicable platform to unify cost-effective whole cell catalysis with biohybrid catalysis. An inactivated esterase autotransporter is employed to display the nitrobindin protein scaffold with a Rh catalyst on the E. coli surface. Stereoselective polymerization of phenylacetylene yielded a high turnover number (TON) (39 × 106 cell–1) for the ArMt bugs conversion platform.
Host protein: Nitrobindin variant NB4Optimization: ---Max TON: 3046ee: ---PDB: ---Notes: Calculated in vivo TON assuming 12800 metalloenzymes per E. coli cell
Directed Evolution of Hybrid Enzymes: Evolving Enantioselectivity of an Achiral Rh-Complex Anchored to a Protein
Chem. Commun. 2006, 4318, 10.1039/b610461d
The concept of utilizing the methods of directed evolution for tuning the enantioselectivity of synthetic achiral metal–ligand centers anchored to proteins has been implemented experimentally for the first time.
Host protein: Streptavidin (Sav)Anchoring strategy: SupramolecularMax TON: 4500ee: 65PDB: ---Notes: ---
Rhodium-Complex-Linked Hybrid Biocatalyst: Stereo-Controlled Phenylacetylene Polymerization within an Engineered Protein Cavity
ChemCatChem 2014, n/a-n/a, 10.1002/cctc.201301055
The incorporation of a Rh complex with a maleimide moiety into the cavity of the nitrobindin β‐barrel scaffold by a covalent linkage at the 96‐position (Cys) provides a hybrid biocatalyst that promotes the polymerization of phenylacetylene. The appropriate structural optimization of the cavity by mutagenesis enhances the stereoselectivity of the polymer with a trans content of 82 % at 25 °C and pH 8.0. The X‐ray crystal structure of one of the hybrid biocatalysts at a resolution of 2.0 Å reveals that the Rh complex is located in the β‐barrel cavity without any perturbation to the total protein structure. Crystal structure analysis and molecular modeling support the fact that the stereoselectivity is enhanced by the effective control of monomer access to the Rh complex within the limited space of the protein cavity.
Host protein: Nitrobindin (Nb)Max TON: ---ee: ---PDB: 3WJCNotes: ---
Stereoselective Hydrogenation of Olefins Using Rhodium-Substituted Carbonic Anhydrase—A New Reductase
Chem. - Eur. J. 2009, 15, 1370-1376, 10.1002/chem.200801673
One useful synthetic reaction missing from nature's toolbox is the direct hydrogenation of substrates using hydrogen. Instead nature uses cofactors like NADH to reduce organic substrates, which adds complexity and cost to these reductions. To create an enzyme that can directly reduce organic substrates with hydrogen, researchers have combined metal hydrogenation catalysts with proteins. One approach is an indirect link where a ligand is linked to a protein and the metal binds to the ligand. Another approach is direct linking of the metal to protein, but nonspecific binding of the metal limits this approach. Herein, we report a direct hydrogenation of olefins catalyzed by rhodium(I) bound to carbonic anhydrase (CA‐[Rh]). We minimized nonspecific binding of rhodium by replacing histidine residues on the protein surface using site‐directed mutagenesis or by chemically modifying the histidine residues. Hydrogenation catalyzed by CA‐[Rh] is slightly slower than for uncomplexed rhodium(I), but the protein environment induces stereoselectivity favoring cis‐ over trans‐stilbene by about 20:1. This enzyme is the first cofactor‐independent reductase that reduces organic molecules using hydrogen. This catalyst is a good starting point to create variants with tailored reactivity and selectivity. This strategy to insert transition metals in the active site of metalloenzymes opens opportunities to a wider range of enzyme‐catalyzed reactions.
Ligand type: CODHost protein: Bovine carbonic anhydrase II (CA)Anchoring strategy: Metal substitutionMax TON: 15.8ee: ---PDB: ---Notes: ---
Ligand type: CODHost protein: Human carbonic anhydrase II (hCAII)Anchoring strategy: Metal substitutionMax TON: 80.5ee: ---PDB: 4CACNotes: PDB ID 4CAC = Structure of Zn containing hCAII
Synthesis of Hybrid Transition-Metalloproteins via Thiol-Selective Covalent Anchoring of Rh-Phosphine and Ru-Phenanthroline Complexes
Dalton Trans. 2010, 39, 8477, 10.1039/c0dt00239a
The preparation of hybrid transition metalloproteins by thiol-selective incorporation of organometallic rhodium- and ruthenium complexes is described. Phosphine ligands and two rhodium-diphosphine complexes bearing a carboxylic acid group were coupled to the cysteine of PYP R52G, yielding a metalloenzyme active in the rhodium catalyzed hydrogenation of dimethyl itaconate. The successful coupling was shown by 31P NMR spectroscopy and ESI mass spectroscopy. In addition wild-type PYP (PYP WT), PYP R52G and ALBP were successfully modified with a (η6-arene) ruthenium(II) phenanthroline complex via a maleimide linker.
Host protein: Photoactive Yellow Protein (PYP)Anchoring strategy: CovalentOptimization: ---Max TON: ---ee: ---PDB: 2PHYNotes: ---