45 publications

45 publications

A Chaperonin as Protein Nanoreactor for Atom-Transfer Radical Polymerization

Bruns, N.

Angew. Chem. Int. Ed. 2014, 53, 1443-1447, 10.1002/anie.201306798

The group II chaperonin thermosome (THS) from the archaea Thermoplasma acidophilum is reported as nanoreactor for atom‐transfer radical polymerization (ATRP). A copper catalyst was entrapped into the THS to confine the polymerization into this protein cage. THS possesses pores that are wide enough to release polymers into solution. The nanoreactor favorably influenced the polymerization of N‐isopropyl acrylamide and poly(ethylene glycol)methylether acrylate. Narrowly dispersed polymers with polydispersity indices (PDIs) down to 1.06 were obtained in the protein nanoreactor, while control reactions with a globular protein–catalyst conjugate only yielded polymers with PDIs above 1.84.


Metal: Cu
Host protein: Thermosome (THS)
Anchoring strategy: Covalent
Optimization: ---
Reaction: Polymerization
Max TON: ---
ee: ---
PDB: ---
Notes: Non-ROMP

A Clamp-Like Biohybrid Catalyst for DNA Oxidation

Nolte, R.J.M.

Nat. Chem. 2013, 5, 945-951, 10.1038/NCHEM.1752

In processive catalysis, a catalyst binds to a substrate and remains bound as it performs several consecutive reactions, as exemplified by DNA polymerases. Processivity is essential in nature and is often mediated by a clamp-like structure that physically tethers the catalyst to its (polymeric) template. In the case of the bacteriophage T4 replisome, a dedicated clamp protein acts as a processivity mediator by encircling DNA and subsequently recruiting its polymerase. Here we use this DNA-binding protein to construct a biohybrid catalyst. Conjugation of the clamp protein to a chemical catalyst with sequence-specific oxidation behaviour formed a catalytic clamp that can be loaded onto a DNA plasmid. The catalytic activity of the biohybrid catalyst was visualized using a procedure based on an atomic force microscopy method that detects and spatially locates oxidized sites in DNA. Varying the experimental conditions enabled switching between processive and distributive catalysis and influencing the sliding direction of this rotaxane-like catalyst.


Metal: Mn
Ligand type: Porphyrin
Host protein: gp45
Anchoring strategy: Covalent
Optimization: ---
Max TON: ---
ee: ---
PDB: 1CZD
Notes: ---

A Cofactor Approach to Copper-Dependent Catalytic Antibodies

Janda, K.D.; Nicholas, K.M.

Proc. Natl. Acad. Sci. U. S. A. 2002, 99, 2648-2653, 10.1073/pnas.052001099

A strategy for the preparation of semisynthetic copper(II)-based catalytic metalloproteins is described in which a metal-binding bis-imidazole cofactor is incorporated into the combining site of the aldolase antibody 38C2. Antibody 38C2 features a large hydrophobic-combining site pocket with a highly nucleophilic lysine residue, LysH93, that can be covalently modified. A comparison of several lactone and anhydride reagents shows that the latter are the most effective and general derivatizing agents for the 38C2 Lys residue. A bis-imidazole anhydride (5) was efficiently prepared from N-methyl imidazole. The 38C2–5-Cu conjugate was prepared by either (i) initial derivatization of 38C2 with 5 followed by metallation with CuCl2, or (ii) precoordination of 5 with CuCl2 followed by conjugation with 38C2. The resulting 38C2–5-Cu conjugate was an active catalyst for the hydrolysis of the coordinating picolinate ester 11, following Michaelis–Menten kinetics [kcat(11) = 2.3 min−1 and Km(11) 2.2 mM] with a rate enhancement [kcat(11)kuncat(11)] of 2.1 × 105. Comparison of the second-order rate constants of the modified 38C2 and the Cu(II)-bis-imidazolyl complex k(6-CuCl2) gives a rate enhancement of 3.5 × 104 in favor of the antibody complex with an effective molarity of 76.7 M, revealing a significant catalytic benefit to the binding of the bis-imidazolyl ligand into 38C2.


Metal: Cu
Ligand type: Bisimidazol
Host protein: Antibody 38C2
Anchoring strategy: Covalent
Optimization: Genetic
Max TON: ---
ee: ---
PDB: ---
Notes: ---

A General Method for Artificial Metalloenzyme Formationthrough Strain-Promoted Azide–Alkyne Cycloaddition

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.


Metal: Rh
Ligand type: Poly-carboxylic acid
Host protein: tHisF
Anchoring strategy: Covalent
Optimization: ---
Reaction: Cyclopropanation
Max TON: 81
ee: ---
PDB: 1THF
Notes: ---

Metal: Rh
Ligand type: Poly-carboxylic acid
Host protein: tHisF
Anchoring strategy: Covalent
Optimization: ---
Reaction: Si-H insertion
Max TON: 7
ee: ---
PDB: 1THF
Notes: ---

A Highly Active Biohybrid Catalyst for Olefin Metathesis in Water: Impact of a Hydrophobic Cavity in a β-Barrel Protein

Okuda, J.

ACS Catal. 2015, 5, 7519-7522, 10.1021/acscatal.5b01792

A series of Grubbs–Hoveyda type catalyst precursors for olefin metathesis containing a maleimide moiety in the backbone of the NHC ligand was covalently incorporated in the cavity of the β-barrel protein nitrobindin. By using two protein mutants with different cavity sizes and choosing the suitable spacer length, an artificial metalloenzyme for olefin metathesis reactions in water in the absence of any organic cosolvents was obtained. High efficiencies reaching TON > 9000 in the ROMP of a water-soluble 7-oxanorbornene derivative and TON > 100 in ring-closing metathesis (RCM) of 4,4-bis(hydroxymethyl)-1,6-heptadiene in water under relatively mild conditions (pH 6, T = 25–40 °C) were observed.


Metal: Ru
Ligand type: Carbene
Host protein: Nitrobindin (Nb)
Anchoring strategy: Covalent
Optimization: Chemical
Reaction: Olefin metathesis
Max TON: 9900
ee: ---
PDB: ---
Notes: ROMP (cis/trans: 48/52)

Metal: Ru
Ligand type: Carbene
Host protein: Nitrobindin (Nb)
Anchoring strategy: Covalent
Optimization: Chemical
Reaction: Olefin metathesis
Max TON: 100
ee: ---
PDB: ---
Notes: RCM

A Hybrid Ring- Opening Metathesis Polymerization Catalyst Based on an Engineered Variant of the Beta-Barrel Protein FhuA

Okuda, J.; Schwaneberg, U.

Chem. - Eur. J. 2013, 19, 13865-13871, 10.1002/chem.201301515

A β‐barrel protein hybrid catalyst was prepared by covalently anchoring a Grubbs–Hoveyda type olefin metathesis catalyst at a single accessible cysteine amino acid in the barrel interior of a variant of β‐barrel transmembrane protein ferric hydroxamate uptake protein component A (FhuA). Activity of this hybrid catalyst type was demonstrated by ring‐opening metathesis polymerization of a 7‐oxanorbornene derivative in aqueous solution.


Metal: Ru
Ligand type: Carbene
Host protein: FhuA ΔCVFtev
Anchoring strategy: Covalent
Optimization: Chemical
Reaction: Olefin metathesis
Max TON: 955
ee: ---
PDB: ---
Notes: ROMP

A Metal Ion Regulated Artificial Metalloenzyme

Roelfes, G.

Dalton Trans. 2017, 46, 4325-4330, 10.1039/C7DT00533D

An artificial metalloenzyme containing both a regulatory and a catalytic domain is selectively activated in presence of Fe2+ ions.


Metal: Fe
Ligand type: Bypyridine
Host protein: LmrR
Anchoring strategy: Covalent
Optimization: Genetic
Max TON: 14
ee: 75
PDB: ---
Notes: ---

Metal: Zn
Ligand type: Bypyridine
Host protein: LmrR
Anchoring strategy: Covalent
Optimization: Genetic
Max TON: 6
ee: 80
PDB: ---
Notes: ---

An Artificial Enzyme Made by Covalent Grafting of an FeII Complex into β-Lactoglobulin: Molecular Chemistry, Oxidation Catalysis, and Reaction-Intermediate Monitoring in a Protein

Banse, F.; Mahy, J.-P.

Chem. - Eur. J. 2015, 21, 12188-12193, 10.1002/chem.201501755

An artificial metalloenzyme based on the covalent grafting of a nonheme FeII polyazadentate complex into bovine β‐lactoglobulin has been prepared and characterized by using various spectroscopic techniques. Attachment of the FeII catalyst to the protein scaffold is shown to occur specifically at Cys121. In addition, spectrophotometric titration with cyanide ions based on the spin‐state conversion of the initial high spin (S=2) FeII complex into a low spin (S=0) one allows qualitative and quantitative characterization of the metal center’s first coordination sphere. This biohybrid catalyst activates hydrogen peroxide to oxidize thioanisole into phenylmethylsulfoxide as the sole product with an enantiomeric excess of up to 20 %. Investigation of the reaction between the biohybrid system and H2O2 reveals the generation of a high spin (S=5/2) FeIII(η2‐O2) intermediate, which is proposed to be responsible for the catalytic sulfoxidation of the substrate.


Metal: Fe
Ligand type: Poly-pyridine
Host protein: ß-lactoglobulin
Anchoring strategy: Covalent
Optimization: ---
Reaction: Sulfoxidation
Max TON: 5.6
ee: 20
PDB: ---
Notes: ---

An Artificial Metalloenzyme for Olefin Metathesis

Hilvert, D.; Ward, T.R.

Chem. Commun. 2011, 47, 12068, 10.1039/c1cc15005g

A Grubbs–Hoveyda type olefin metathesis catalyst, equipped with an electrophilic bromoacetamide group, was used to modify a cysteine-containing variant of a small heat shock protein from Methanocaldococcus jannaschii. The resulting artificial metalloenzyme was found to be active under acidic conditions in a benchmark ring closing metathesis reaction.


Metal: Ru
Ligand type: Carbene
Anchoring strategy: Covalent
Optimization: ---
Reaction: Olefin metathesis
Max TON: 25
ee: ---
PDB: ---
Notes: RCM

An Enantioselective Artificial Metallo-Hydratase

Roelfes, G.

Chem. Sci. 2013, 4, 3578, 10.1039/c3sc51449h

Direct addition of water to alkenes to generate important chiral alcohols as key motif in a variety of natural products still remains a challenge in organic chemistry. Here, we report the first enantioselective artificial metallo-hydratase, based on the transcription factor LmrR, which catalyses the conjugate addition of water to generate chiral β-hydroxy ketones with enantioselectivities up to 84% ee. A mutagenesis study revealed that an aspartic acid and a phenylalanine located in the active site play a key role in achieving efficient catalysis and high enantioselectivities.


Metal: Cu
Ligand type: Phenanthroline
Host protein: LmrR
Anchoring strategy: Covalent
Optimization: Genetic
Max TON: 30
ee: 84
PDB: 3F8B
Notes: ---

Aqueous Phase Transfer Hydrogenation of Aryl Ketones Catalysed by Achiral Ruthenium(II) and Rhodium(III) Complexes and their Papain Conjugates

Salmain, M.

Appl. Organomet. Chem. 2013, 27, 6-12, 10.1002/aoc.2929

Several ruthenium and rhodium complexes including 2,2′‐dipyridylamine ligands substituted at the central N atom by an alkyl chain terminated by a maleimide functional group were tested along with a newly synthesized Rh(III) complex of unsubstituted 2,2′‐dipyridylamine as catalysts in the transfer hydrogenation of aryl ketones in neat water with formate as hydrogen donor. All of them except one led to the secondary alcohol products with conversion rates depending on the metal complex. Site‐specific anchoring of the N‐maleimide complexes to the single free cysteine residue of the cysteine endoproteinase papain endowed this protein with transfer hydrogenase properties towards 2,2,2‐trifluoroacetophenone. Quantitative conversions were reached with the Rh‐based biocatalysts, while modest enantioselectivities were obtained in certain reactional conditions.


Metal: Rh
Ligand type: Cp*; Poly-pyridine
Host protein: Papain (PAP)
Anchoring strategy: Covalent
Optimization: Chemical
Reaction: Hydrogenation
Max TON: 96
ee: 15
PDB: ---
Notes: ---

Artificial Copper Enzymes for Asymmetric Diels–AlderReactions

Kamer, P.C.J.; Laan, W.

ChemCatChem 2013, 5, 1184-1191, 10.1002/cctc.201200671

The development of artificial copper enzymes from sterol carrier protein type 2 like domain (SCP‐2L) for the use in asymmetric catalysis was explored. For this purpose, proteins were modified with various nitrogen donor ligands. Maleimide‐containing ligands were found most suitable for selective cysteine bio‐conjugation. Fluorescence spectroscopy was used to confirm copper binding to an introduced phenanthroline ligand, which was introduced in two unique cysteine containing SCP‐2L mutants. Copper adducts of several modified SCP‐2L templates were applied in asymmetric Diels–Alder reactions. A clear influence of both the protein environment and the introduced ligand was found in the asymmetric Diels–Alder reaction between azachalcone and cyclopentadiene. A promising enantioselectivity of 25 % ee was obtained by using SCP‐2L V83C modified with phenanthroline–maleimide ligand. Good endo selectivity was observed for SCP‐2L modified with the dipicolylamine‐based nitrogen donor ligand. These artificial metalloenzymes provide a suitable starting point for the implementation of various available techniques to optimise the performance of this system.


Metal: Cu
Anchoring strategy: Covalent
Optimization: Chemical & genetic
Max TON: 9.6
ee: 25
PDB: 1IKT
Notes: ---

Artificial Heme Enzymes for the Construction of Gold-Based Biomaterials

Lombardi, A.; Nastri, F.

Int. J. Mol. Sci. 2018, 19, 2896, 10.3390/ijms19102896

Many efforts are continuously devoted to the construction of hybrid biomaterials for specific applications, by immobilizing enzymes on different types of surfaces and/or nanomaterials. In addition, advances in computational, molecular and structural biology have led to a variety of strategies for designing and engineering artificial enzymes with defined catalytic properties. Here, we report the conjugation of an artificial heme enzyme (MIMO) with lipoic acid (LA) as a building block for the development of gold-based biomaterials. We show that the artificial MIMO@LA can be successfully conjugated to gold nanoparticles or immobilized onto gold electrode surfaces, displaying quasi-reversible redox properties and peroxidase activity. The results of this work open interesting perspectives toward the development of new totally-synthetic catalytic biomaterials for application in biotechnology and biomedicine, expanding the range of the biomolecular component aside from traditional native enzymes.


Metal: Fe
Ligand type: Amino acid; Porphyrin
Anchoring strategy: Covalent
Optimization: Chemical & genetic
Reaction: Oxidation
Max TON: ---
ee: ---
PDB: ---
Notes: Immobilization of the ArM on gold surfaces via a lipoic acid anchor.

Artificial Metalloenzymes based on Protein Cavities: Exploring the Effect of Altering the Metal Ligand Attachment Position by Site Directed Mutagenesis

Distefano, M.D.

Bioorg. Med. Chem. Lett. 1999, 9, 79-84, 10.1016/S0960-894X(98)00684-2

In an effort to construct catalysts with enzyme-like properties, we are employing a small, cavity-containing protein as a scaffold for the attachment of catalytic groups. In earlier work we demonstrated that a phenanthroline ligand could be introduced into the cavity of the protein ALBP and used to catalyze ester hydrolysis. To examine the effect of positioning the phenanthroline catalyst at different locations wthin the protein cavity, three new constucts — Phen60, Phen72 and Phen104 — were prepared. Each new conjugate was characterized by UV/vis spectroscopy, fluorescence spectroscopy, guanidine hydrochloride denaturation, gel filtration chromatography, and CD spectroscopy to confirm the preparation of the desired contruct. Analysis of reactions containing Ala-OiPr showed that Phen60 catalyzed ester hydrolysis with less selectivity than ALBP-Phen while Phen72 promoted this same reaction with higher selectivity. Reactions with Tyr-OMe were catalyzed with higher selectivity by Phen60 and more rapidly by Phen104. These results demonstrate that both the rates and selectivities of hydrolysis reactions catalyzed by these constructs are dependent on the precise site of attachment of the metal ligand within the protein cavity.


Metal: Cu
Ligand type: Phenanthroline
Anchoring strategy: Covalent
Optimization: Genetic
Max TON: 1 to 4
ee: 61 to 94
PDB: ---
Notes: Varied attachment position

Artificial Metalloenzymes Through Cysteine-Selective Conjugation of Phosphines to Photoactive Yellow Protein

Kamer, P.C.J.

ChemBioChem 2010, 11, 1236-1239, 10.1002/cbic.201000159

Pinning phosphines on proteins: A method for the cysteine‐selective bioconjugation of phosphines has been developed. The photoactive yellow protein has been site‐selectively functionalized with phosphine ligands and phosphine transition metal complexes to afford artificial metalloenzymes that are active in palladium‐catalysed allylic nucleophilic substitution reactions.


Metal: Pd
Ligand type: Allyl; Phosphine
Anchoring strategy: Covalent
Optimization: Chemical & genetic
Reaction: Allylic amination
Max TON: 45
ee: ---
PDB: 2PHY
Notes: ---

A Semisynthetic Metalloenzyme based on a Protein Cavity that Catalyzes the Enantioselective Hydrolysis of Ester and Amide Substrates

Distefano, M.D.

J. Am. Chem. Soc. 1997, 119, 11643-11652, 10.1021/JA970820K

In an effort to prepare selective and efficient catalysts for ester and amide hydrolysis, we are designing systems that position a coordinated metal ion within a defined protein cavity. Here, the preparation of a protein-1,10-phenanthroline conjugate and the hydrolytic chemistry catalyzed by this construct are described. Iodoacetamido-1,10-phenanthroline was used to modify a unique cysteine residue in ALBP (adipocyte lipid binding protein) to produce the conjugate ALBP-Phen. The resulting material was characterized by electrospray mass spectrometry, UV/vis and fluorescence spectroscopy, gel filtration chromatography, and thiol titration. The stability of ALBP-Phen was evaluated by guanidine hydrochloride denaturation experiments, and the ability of the conjugate to bind Cu(II) was demonstrated by fluorescence spectroscopy. ALBP-Phen-Cu(II) catalyzes the enantioselective hydrolysis of several unactivated amino acid esters under mild conditions (pH 6.1, 25 °C) at rates 32−280-fold above the background rate in buffered aqueous solution. In 24 h incubations 0.70 to 7.6 turnovers were observed with enantiomeric excesses ranging from 31% ee to 86% ee. ALBP-Phen-Cu(II) also promotes the hydrolysis of an aryl amide substrate under more vigorous conditions (pH 6.1, 37 °C) at a rate 1.6 × 104-fold above the background rate. The kinetics of this amide hydrolysis reaction fit the Michaelis−Menten relationship characteristic of enzymatic processes. The rate enhancements for ester and amide hydrolysis reported here are 102−103 lower than those observed for free Cu(II) but comparable to those previously reported for Cu(II) complexes.


Metal: Cu
Ligand type: Phenanthroline
Anchoring strategy: Covalent
Optimization: ---
Max TON: 1 to 8
ee: 39 to 86
PDB: ---
Notes: ---

A Site-Selective Dual Anchoring Strategy for Artificial Metalloprotein Design

Lu, Y.

J. Am. Chem. Soc. 2004, 126, 10812-10813, 10.1021/ja046908x

Introducing nonnative metal ions or metal-containing prosthetic groups into a protein can dramatically expand the repertoire of its functionalities and thus its range of applications. Particularly challenging is the control of substrate-binding and thus reaction selectivity such as enantioselectivity. To meet this challenge, both non-covalent and single-point attachments of metal complexes have been demonstrated previously. Since the protein template did not evolve to bind artificial metal complexes tightly in a single conformation, efforts to restrict conformational freedom by modifying the metal complexes and/or the protein are required to achieve high enantioselectivity using the above two strategies. Here we report a novel site-selective dual anchoring (two-point covalent attachment) strategy to introduce an achiral manganese salen complex (Mn(salen)), into apo sperm whale myoglobin (Mb) with bioconjugation yield close to 100%. The enantioselective excess increases from 0.3% for non-covalent, to 12.3% for single point, and to 51.3% for dual anchoring attachments. The dual anchoring method has the advantage of restricting the conformational freedom of the metal complex in the protein and can be generally applied to protein incorporation of other metal complexes with minimal structural modification to either the metal complex or the protein.


Metal: Mn
Ligand type: Salen
Host protein: Myoglobin (Mb)
Anchoring strategy: Covalent
Optimization: Genetic
Reaction: Sulfoxidation
Max TON: 3.9
ee: 51
PDB: 1MBO
Notes: Sperm whale myoglobin

Autoxidation of Ascorbic Acid Catalyzed by a Semisynthetic Enzyme

Kaiser, E.T.

Biopolymers 1990, 29, 39-43, 10.1002/bip.360290107

The semisyntehtic enzyme 6 was prepared by alkylation of the cysteine‐25 sulfhydryl group of papain with the bipyridine 5 and was shown to stoichiometrically bind copper ion; 7 catalyzed the autoxidation of ascorbic acid derivatives with saturation kinetics approximately 20‐fold faster than a model system using 3‐Cu(II).


Metal: Cu
Ligand type: Bipyridine
Host protein: Papain (PAP)
Anchoring strategy: Covalent
Optimization: ---
Reaction: Oxidation
Max TON: ---
ee: ---
PDB: ---
Notes: ---

Chemical Conversion of a DNA-Binding Protein into a Site-Specific Nuclease

Sigman, D.S.

Science 1987, 237, 1197-1201, 10.1126/science.2820056

The tryptophan gene (trp) repressor of Escherichia coli has been converted into a site-specific nuclease by covalently attaching it to the 1,10-phenanthroline-copper complex. In its cuprous form, the coordination complex with hydrogen peroxide as a coreactant cleaves DNA by oxidatively attacking the deoxyribose moiety. The chemistry for the attachment of 1,10-phenanthroline to the trp repressor involves modification of lysyl residues with iminothiolane followed by alkylation of the resulting sulfhydryl groups with 5-iodoacetamido-1,10-phenanthroline. The modified trp repressor cleaves the operators of aroH and trpEDCBA upon the addition of cupric ion and thiol in a reaction dependent on the corepressor L-tryptophan. Scission was restricted to the binding site for the repressor, defined by deoxyribonuclease I footprinting. Since DNA-binding proteins have recognition sequences approximately 20 base pairs long, the nucleolytic activities derived from them could be used to isolate long DNA fragments for sequencing or chromosomal mapping.


Metal: Cu
Ligand type: Phenanthroline
Anchoring strategy: Covalent
Optimization: ---
Reaction: Oxidative cleavage
Max TON: <1
ee: ---
PDB: ---
Notes: Engineered sequence specificity

Chemically Engineered Papain as Artificial Formate Dehydrogenase for NAD(P)H Regeneration

Salmain, M.

Org. Biomol. Chem. 2011, 9, 5720, 10.1039/c1ob05482a

Organometallic complexes of the general formula [(η6-arene)Ru(N⁁N)Cl]+ and [(η5-Cp*)Rh(N⁁N)Cl]+ where N⁁N is a 2,2′-dipyridylamine (DPA) derivative carrying a thiol-targeted maleimide group, 2,2′-bispyridyl (bpy), 1,10-phenanthroline (phen) or ethylenediamine (en) and arene is benzene, 2-chloro-N-[2-(phenyl)ethyl]acetamide or p-cymene were identified as catalysts for the stereoselective reduction of the enzyme cofactors NAD(P)+ into NAD(P)H with formate as a hydride donor. A thorough comparison of their effectiveness towards NAD+ (expressed as TOF) revealed that the RhIII complexes were much more potent catalysts than the RuII complexes. Within the RuII complex series, both the N⁁N and arene ligands forming the coordination sphere had a noticeable influence on the activity of the complexes. Covalent anchoring of the maleimide-functionalized RuII and RhIII complexes to the cysteine endoproteinase papain yielded hybrid metalloproteins, some of them displaying formate dehydrogenase activity with potentially interesting kinetic parameters.


Metal: Rh
Ligand type: Cp*; Poly-pyridine
Host protein: Papain (PAP)
Anchoring strategy: Covalent
Optimization: Chemical
Reaction: Hydrogenation
Max TON: ---
ee: ---
PDB: ---
Notes: TOF = 52.1 h-1 for NAD+

Conversion of a Helix-Turn-Helix Motif Sequence-Specific DNA Binding Protein into a Site-Specific DNA Cleavage Agent

Ebright, R.H.; Gunasekeram, A.

Proc. Natl. Acad. Sci. U. S. A. 1990, 87, 2882-2886, 10.1073/pnas.87.8.2882

Escherichia coli catabolite gene activator protein (CAP) is a helix-turn-helix motif sequence-specific DNA binding protein [de Crombrugghe, B., Busby, S. & Buc, H. (1984) Science 224, 831-838; and Pabo, C. & Sauer, R. (1984) Annu. Rev. Biochem. 53, 293-321]. In this work, CAP has been converted into a site-specific DNA cleavage agent by incorporation of the chelator 1,10-phenanthroline at amino acid 10 of the helix-turn-helix motif. [(N-Acetyl-5-amino-1,10-phenanthroline)-Cys178]CAP binds to a 22-base-pair DNA recognition site with Kobs = 1 x 10(8) M-1. In the presence of Cu(II) and reducing agent, [(N-acetyl-5-amino-1,10-phenanthroline)-Cys178]CAP cleaves DNA at four adjacent nucleotides on each DNA strand within the DNA recognition site. The DNA cleavage reaction has been demonstrated using 40-base-pair and 7164-base-pair DNA substrates. The DNA cleavage reaction is not inhibited by dam methylation of the DNA substrate. Such semisynthetic site-specific DNA cleavage agents have potential applications in chromosome mapping, cloning, and sequencing.


Metal: Cu
Ligand type: Phenanthroline
Anchoring strategy: Covalent
Optimization: ---
Reaction: Oxidative cleavage
Max TON: <1
ee: ---
PDB: ---
Notes: Engineered sequence specificity

Covalent Anchoring of a Racemization Catalyst to CALB-Beads: Towards Dual Immobilization of DKR Catalysts

Klein Gebbink, R.J.M.; van Koten, G.

Tetrahedron Lett. 2011, 52, 1601-1604, 10.1016/j.tetlet.2011.01.106

The preparation of a heterogeneous bifunctional catalytic system, combining the catalytic properties of an organometallic catalyst (racemization) with those of an enzyme (enantioselective acylation) is described. A novel ruthenium phosphonate inhibitor was synthesized and covalently anchored to a lipase immobilized on a solid support (CALB, Novozym® 435). The immobilized bifunctional catalytic system showed activity in both racemization of (S)-1-phenylethanol and selective acylation of 1-phenylethanol.


Metal: Ru
Anchoring strategy: Covalent
Optimization: Chemical
Reaction: Acylation
Max TON: ---
ee: >99%
PDB: ---
Notes: Lipase CALB is immobilized on a solid support (Novozym®435). Dynamic kinetic resolution (DKR) of 1-phenylethanol to the acylated product.

Creation of an Artificial Metalloprotein with a Hoveyda–Grubbs Catalyst Moiety through the Intrinsic Inhibition Mechanism of α-Chymotrypsin

Chem. Commun. 2012, 48, 1662, 10.1039/c2cc16898g

An L-phenylalanyl chloromethylketone-based inhibitor equipped with a Hoveyda–Grubbs catalyst moiety was regioselectively incorporated into the cleft of α-chymotrypsin through the intrinsic inhibition mechanism of the protein to construct an artificial organometallic protein.


Metal: Ru
Ligand type: Carbene
Host protein: α-chymotrypsin
Anchoring strategy: Covalent
Optimization: ---
Reaction: Olefin metathesis
Max TON: 20
ee: ---
PDB: ---
Notes: RCM

Enantioselective Artificial Metalloenzymes by Creation of a Novel Active Site at the Protein Dimer Interface

Roelfes, G.

Angew. Chem. Int. Ed. 2012, 51, 7472-7475, 10.1002/anie.201202070

A game of two halves: Artificial metalloenzymes are generated by forming a novel active site on the dimer interface of the transcription factor LmrR. Two copper centers are incorporated by binding to ligands in each half of the dimer. With this system up to 97 % ee was obtained in the benchmark CuII catalyzed Diels–Alder reaction (see scheme).


Metal: Cu
Ligand type: Bipyridine; Phenanthroline
Host protein: LmrR
Anchoring strategy: Covalent
Optimization: Genetic
Max TON: 32.7
ee: 97
PDB: 3F8B
Notes: ---

Engineering a Dirhodium Artificial Metalloenzyme for Selective Olefin Cyclopropanation

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.


Metal: Rh
Ligand type: Poly-carboxylic acid
Anchoring strategy: Covalent
Optimization: Chemical & genetic
Reaction: Cyclopropanation
Max TON: 74
ee: 92
PDB: ---
Notes: ---

Evolving Artificial Metalloenzymes via Random Mutagenesis

Lewis, J.C.

Nat. Chem. 2018, 10, 318-324, 10.1038/nchem.2927

Random mutagenesis has the potential to optimize the efficiency and selectivity of protein catalysts without requiring detailed knowledge of protein structure; however, introducing synthetic metal cofactors complicates the expression and screening of enzyme libraries, and activity arising from free cofactor must be eliminated. Here we report an efficient platform to create and screen libraries of artificial metalloenzymes (ArMs) via random mutagenesis, which we use to evolve highly selective dirhodium cyclopropanases. Error-prone PCR and combinatorial codon mutagenesis enabled multiplexed analysis of random mutations, including at sites distal to the putative ArM active site that are difficult to identify using targeted mutagenesis approaches. Variants that exhibited significantly improved selectivity for each of the cyclopropane product enantiomers were identified, and higher activity than previously reported ArM cyclopropanases obtained via targeted mutagenesis was also observed. This improved selectivity carried over to other dirhodium-catalysed transformations, including N–H, S–H and Si–H insertion, demonstrating that ArMs evolved for one reaction can serve as starting points to evolve catalysts for others.


Metal: Rh
Ligand type: OAc
Anchoring strategy: Covalent
Optimization: Chemical & genetic
Reaction: Cyclopropanation
Max TON: 66
ee: 94
PDB: 5T88
Notes: Mutagenesis of the ArM by error-prone PCR

Metal: Rh
Ligand type: OAc
Anchoring strategy: Covalent
Optimization: Chemical & genetic
Reaction: N-H Insertion
Max TON: 73
ee: 40
PDB: 5T88
Notes: Mutagenesis of the ArM by error-prone PCR

Metal: Rh
Ligand type: OAc
Anchoring strategy: Covalent
Optimization: Chemical & genetic
Reaction: S-H insertion
Max TON: 64
ee: 32
PDB: 5T88
Notes: Mutagenesis of the ArM by error-prone PCR

Metal: Rh
Ligand type: OAc
Anchoring strategy: Covalent
Optimization: Chemical & genetic
Reaction: Si-H insertion
Max TON: 35
ee: 64
PDB: 5T88
Notes: Mutagenesis of the ArM by error-prone PCR

Helichrome: Synthesis and Enzymatic Activity of a Designed Hemeprotein

Kaiser, E.T.; Sasaki, T.

J. Am. Chem. Soc. 1989, 111, 380-381, 10.1021/ja00183a065

n/a


Metal: Fe
Ligand type: Porphyrin
Host protein: Artificial construct
Anchoring strategy: Covalent
Optimization: ---
Max TON: ---
ee: ---
PDB: ---
Notes: Only 60 amino acids

Hybrid Ruthenium ROMP Catalysts Based on an Engineered Variant of β-Barrel Protein FhuA ΔCVFtev: Effect of Spacer Length

Okuda, J.

Chem. - Asian J. 2015, 10, 177-182, 10.1002/asia.201403005

A biohybrid ring‐opening olefin metathesis polymerization catalyst based on the reengineered β‐barrel protein FhuA ΔCVFtev was chemically modified with respect to the covalently anchored Grubbs–Hoveyda type catalyst. Shortening of the spacer (1,3‐propanediyl to methylene) between the N‐heterocyclic carbene ligand and the cysteine site 545 increased the ROMP activity toward a water‐soluble 7‐oxanorbornene derivative. The cis/trans ratio of the double bond in the polymer was influenced by the hybrid catalyst.


Metal: Ru
Ligand type: Carbene
Host protein: FhuA ΔCVFtev
Anchoring strategy: Covalent
Optimization: Chemical
Reaction: Olefin metathesis
Max TON: 555
ee: ---
PDB: ---
Notes: ROMP; cis/trans = 58/42

Lipase Active Site Covalent Anchoring of Rh(NHC) Catalysts: Towards Chemoselective Artificial Metalloenzymes

Klein Gebbink, R.J.M.

Chem. Commun. 2015, 51, 6792-6795, 10.1039/c4cc09700a

A Rh(NHC) phosphonate complex reacts with the lipases cutinase and Candida antarctica lipase B resulting in the first (soluble) artificial metalloenzymes formed by covalent active site-directed hybridization. When compared to unsupported complexes, these new robust hybrids show enhanced chemoselectivity in the (competitive) hydrogenation of olefins over ketones.


Metal: Rh
Ligand type: Carbene
Host protein: Cutinase
Anchoring strategy: Covalent
Optimization: ---
Reaction: Hydrogenation
Max TON: 20
ee: rac.
PDB: 1CEX
Notes: ---

Metal: Rh
Ligand type: Carbene
Anchoring strategy: Covalent
Optimization: ---
Reaction: Hydrogenation
Max TON: 20
ee: rac.
PDB: 4K6G
Notes: ---

Manganese Terpyridine Artificial Metalloenzymes for Benzylic Oxygenation and Olefin Epoxidation

Lewis, J.C.

Tetrahedron 2014, 70, 4245-4249, 10.1016/j.tet.2014.03.008

New catalysts for non-directed hydrocarbon functionalization have great potential in organic synthesis. We hypothesized that incorporating a Mn-terpyridine cofactor into a protein scaffold would lead to artificial metalloenzymes (ArMs) in which the selectivity of the Mn cofactor could be controlled by the protein scaffold. We designed and synthesized a maleimide-substituted Mn-terpyridine cofactor and demonstrated that this cofactor could be incorporated into two different scaffold proteins to generate the desired ArMs. The structure and reactivity of one of these ArMs was explored, and the broad oxygenation capability of the Mn-terpyridine catalyst was maintained, providing a robust platform for optimization of ArMs for selective hydrocarbon functionalization.


Metal: Mn
Ligand type: Poly-pyridine
Host protein: Nitrobindin (Nb)
Anchoring strategy: Covalent
Optimization: Chemical
Max TON: 19.2
ee: ---
PDB: 3EMM
Notes: ---

Metal: Mn
Ligand type: Poly-pyridine
Host protein: Nitrobindin (Nb)
Anchoring strategy: Covalent
Optimization: Chemical
Reaction: Epoxidation
Max TON: 19.8
ee: ---
PDB: 3EMM
Notes: ---