11 publications
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A Rhodium Complex-Linked β-Barrel Protein as a Hybrid Biocatalyst for Phenylacetylene Polymerization
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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.
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Artificial Diels–Alderase based on the Transmembrane Protein FhuA
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Beilstein J. Org. Chem. 2016, 12, 1314-1321, 10.3762/bjoc.12.124
Copper(I) and copper(II) complexes were covalently linked to an engineered variant of the transmembrane protein Ferric hydroxamate uptake protein component A (FhuA ΔCVFtev). Copper(I) was incorporated using an N-heterocyclic carbene (NHC) ligand equipped with a maleimide group on the side arm at the imidazole nitrogen. Copper(II) was attached by coordination to a terpyridyl ligand. The spacer length was varied in the back of the ligand framework. These biohybrid catalysts were shown to be active in the Diels–Alder reaction of a chalcone derivative with cyclopentadiene to preferentially give the endo product.
Metal: CuLigand type: TerpyridineHost protein: Ferric hydroxamate uptake protein component: A (FhuA)Anchoring strategy: Cystein-maleimideOptimization: ChemicalNotes: ---
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Artificial Metalloenzymes as Catalysts for Oxidative Lignin Degradation
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ACS Sustainable Chem. Eng. 2018, 6, 15100-15107, 10.1021/acssuschemeng.8b03568
We report novel artificial metalloenzymes (ArMs), containing tris(pyridylmethyl)amine (TPA), for the atom economic oxidation of lignin β-O-4 model compounds, using hydrogen peroxide. The protein scaffold alters the selectivity of the reaction from a low yielding cleavage reaction when using the parent Fe-tpa complex to a high yielding benzylic alcohol oxidation when using the complex incorporated into a protein scaffold, SCP-2L A100C. Engineering the protein scaffold to incorporate glutamic acid was found to improve the ArM activity, showing that rational design of the protein environment using metal binding amino acids can be a first step toward improving the overall activity of an artificial metalloenzyme.
Metal: FeLigand type: Tris(pyridylmethyl)amine (TPA)Host protein: Steroid Carrier Protein 2L (SCP-2L)Anchoring strategy: Cystein-maleimideOptimization: Chemical & geneticNotes: Reaction performed with a lignin model compound and hydrogen peroxide as oxidizing agent
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A Whole Cell E. coli Display Platform for Artificial Metalloenzymes: Poly(phenylacetylene) Production with a Rhodium–Nitrobindin Metalloprotein
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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.
Metal: RhHost protein: Nitrobindin variant NB4Anchoring strategy: Cystein-maleimideOptimization: ---Notes: Calculated in vivo TON assuming 12800 metalloenzymes per E. coli cell
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Construction of a Hybrid Biocatalyst Containing a Covalently-Linked Terpyridine Metal Complex within a Cavity of Aponitrobindin
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J. Inorg. Biochem. 2016, 158, 55-61, 10.1016/j.jinorgbio.2015.12.026
A hybrid biocatalyst containing a metal terpyridine (tpy) complex within a rigid β-barrel protein nitrobindin (NB) is constructed. A tpy ligand with a maleimide group, N-[2-([2,2′:6′,2′′-terpyridin]-4′-yloxy)ethyl]maleimide (1), was covalently linked to Cys96 inside the cavity of NB to prepare a conjugate NB–1. Binding of Cu2 +, Zn2 +, or Co2 + ion to the tpy ligand in NB–1 was confirmed by UV–vis spectroscopy and ESI–TOF MS measurements. Cu2 +-bound NB–1 is found to catalyze a Diels–Alder reaction between azachalcone and cyclopentadiene in 22% yield, which is higher than that of the Cu2 +–tpy complex without the NB matrix. The results suggest that the hydrophobic cavity close to the copper active site within the NB scaffold supports the binding of the two substrates, dienophile and diene, to promote the reaction.
Metal: CuLigand type: TerpyridineHost protein: Nitrobindin (Nb)Anchoring strategy: Cystein-maleimideOptimization: ---Notes: ---
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Dual Modification of a Triple-Stranded β-Helix Nanotube with Ru and Re Metal Complexes to Promote Photocatalytic Reduction of CO2
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Chem. Commun. 2011, 47, 2074, 10.1039/C0CC03015E
We have constructed a robust β-helical nanotube from the component proteins of bacteriophage T4 and modified this nanotube with RuII(bpy)3 and ReI(bpy)(CO)3Cl complexes. The photocatalytic system arranged on the tube catalyzes the reduction of CO2 with higher reactivity than that of the mixture of the monomeric forms.
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Metal: RuLigand type: BipyridineHost protein: [(gp5βf)3]2Anchoring strategy: Lysine-succinimideOptimization: GeneticNotes: ---
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Enzyme Activity by Design: An Artificial Rhodium Hydroformylase for Linear Aldehydes
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Angew. Chem. Int. Ed. 2017, 129, 13784-13788, 10.1002/ange.201705753
Metal: RhHost protein: Steroid Carrier Protein 2L (SCP-2L)Anchoring strategy: Cystein-maleimideOptimization: Chemical & geneticNotes: Selectivity for the linear product over the branched product
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Molecular Design of Heteroprotein Assemblies Providing a Bionanocup as a Chemical Reactor
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Small 2008, 4, 50-54, 10.1002/smll.200700855
A bionanocup chemical reactor is constructed from a heteroprotein assembly from bacteriophage T4. The preparation of a stable iron(III) porphyrin–bionanocup composite is described. The hydrophobic cup provides a space suitable for the fixation of low‐water‐solubility iron(III) porphyrins. The application of the iron(III) porphyrin–bionanocup composites for the catalysis of sulfoxidation of thioanisoles is demonstrated (see figure).
Metal: FeLigand type: Maleimide-protoporphyrin IXHost protein: (gp27-gp5)3Anchoring strategy: Cystein-maleimideOptimization: ---Notes: ---
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Photoinduced Electron Transfer within Supramolecular Hemoprotein Co-Assemblies and Heterodimers Containing Fe and Zn Porphyrins
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J. Inorg. Biochem. 2019, 193, 42-51, 10.1016/j.jinorgbio.2019.01.001
Electron transfer (ET) events occurring within metalloprotein complexes are among the most important classes of reactions in biological systems. This report describes a photoinduced electron transfer between Zn porphyrin and Fe porphyrin within a supramolecular cytochrome b562 (Cyt b562) co-assembly or heterodimer with a well-defined rigid structure formed by a metalloporphyrin–heme pocket interaction and a hydrogen-bond network at the protein interface. The photoinduced charge separation (CS: kCS = 320–600 s−1) and subsequent charge recombination (CR: kCR = 580–930 s−1) were observed in both the Cyt b562 co-assembly and the heterodimer. In contrast, interestingly, no ET events were observed in a system comprised of a flexible and structurally-undefined co-assembly and heterodimers which lack the key hydrogen-bond interaction at the protein interface. Moreover, analysis of the kinetic constants of CS and CR of the heterodimer using the Marcus equation suggests that a single-step ET reaction occurs in the system. These findings provide strong support that the rigid hemoprotein-assembling system containing an appropriate hydrogen-bond network at the protein interface is essential for monitoring the ET reaction.
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Rhodium-Complex-Linked Hybrid Biocatalyst: Stereo-Controlled Phenylacetylene Polymerization within an Engineered Protein Cavity
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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.
Metal: RhHost protein: Nitrobindin (Nb)Anchoring strategy: Cystein-maleimideOptimization: GeneticNotes: ---
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Semi-Synthesis of an Artificial Scandium(III) Enzyme with a β-Helical Bio-Nanotube
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Dalton Trans. 2012, 41, 11424, 10.1039/C2DT31030A
We have succeeded in preparing semi-synthesized proteins bound to Sc3+ ion which can promote an epoxide ring-opening reaction. The Sc3+ binding site was created on the surface of [(gp5βf)3]2 (N. Yokoi et al., Small, 2010, 6, 1873) by introducing a cysteine residue for conjugation of a bpy moiety using a thiol–maleimide coupling reaction. Three cysteine mutants [(gp5βf_X)3]2 (X = G18C, L47C, N51C) were prepared to introduce a bpy in different positions because it had been reported that Sc3+ ion can serve as a Lewis-acid catalyst for an epoxide ring-opening reaction upon binding of epoxide to bpy and two –ROH groups. G18C_bpy with Sc3+ can accelerate the rate of catalysis of the epoxide ring-opening reaction and has the highest rate of conversion among the three mutants. The value is more than 20 times higher than that of the mixtures of [(gp5βf)3]2/2,2′-bipyridine and L-threonine/2,2′-bipyridine. The elevated activity was obtained by the cooperative effect of stabilizing the Sc3+ coordination and accumulation of substrates on the protein surface. Thus, we expect that the semi-synthetic approach can provide insights into new rational design of artificial metalloenzymes.
Metal: ScLigand type: BipyridineHost protein: [(gp5βf)3]2Anchoring strategy: Cystein-maleimideOptimization: GeneticNotes: ---