6 publications

6 publications

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: ---

Alteration of the Oxygen-Dependent Reactivity of De Novo Due Ferri Proteins

DeGrado, W.F.

Nat. Chem. 2012, 4, 900-906, 10.1038/NCHEM.1454

De novo proteins provide a unique opportunity to investigate the structure–function relationships of metalloproteins in a minimal, well-defined and controlled scaffold. Here, we describe the rational programming of function in a de novo designed di-iron carboxylate protein from the Due Ferri family. Originally created to catalyse the O2-dependent, two-electron oxidation of hydroquinones, the protein was reprogrammed to catalyse the selective N-hydroxylation of arylamines by remodelling the substrate access cavity and introducing a critical third His ligand to the metal-binding cavity. Additional second- and third-shell modifications were required to stabilize the His ligand in the core of the protein. These structural changes resulted in at least a 106-fold increase in the relative rate between the arylamine N-hydroxylation and hydroquinone oxidation reactions. This result highlights the potential for using de novo proteins as scaffolds for future investigations of the geometric and electronic factors that influence the catalytic tuning of di-iron active sites.


Metal: Fe
Ligand type: Amino acid
Host protein: Due Ferri
Anchoring strategy: Dative
Optimization: Genetic
Reaction: N-Hydroxylation
Max TON: ---
ee: ---
PDB: 2LFD
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

Hydrolytic Catalysis and Structural Stabilization in a Designed Metalloprotein

Pecoraro, V.L.

Nat. Chem. 2012, 4, 118-123, 10.1038/NCHEM.1201

Metal ions are an important part of many natural proteins, providing structural, catalytic and electron transfer functions. Reproducing these functions in a designed protein is the ultimate challenge to our understanding of them. Here, we present an artificial metallohydrolase, which has been shown by X-ray crystallography to contain two different metal ions—a Zn(II) ion, which is important for catalytic activity, and a Hg(II) ion, which provides structural stability. This metallohydrolase displays catalytic activity that compares well with several characteristic reactions of natural enzymes. It catalyses p-nitrophenyl acetate (pNPA) hydrolysis with an efficiency only ~100-fold less than that of human carbonic anhydrase (CA)II and at least 550-fold better than comparable synthetic complexes. Similarly, CO2 hydration occurs with an efficiency within ~500-fold of CAII. Although histidine residues in the absence of Zn(II) exhibit pNPA hydrolysis, miniscule apopeptide activity is observed for CO2 hydration. The kinetic and structural analysis of this first de novo designed hydrolytic metalloenzyme reveals necessary design features for future metalloenzymes containing one or more metals.


Metal: Hg; Zn
Ligand type: Amino acid
Host protein: TRI peptide
Anchoring strategy: Dative
Optimization: Chemical & genetic
Max TON: >10
ee: ---
PDB: 3PBJ
Notes: Zn ion for catalytic activity, Hg ion for structural stability of the ArM. PDB ID 3PBJ = Structure of an analogue.

Metal: Hg; Zn
Ligand type: Amino acid
Host protein: TRI peptide
Anchoring strategy: Dative
Optimization: Chemical & genetic
Max TON: ---
ee: ---
PDB: 3PBJ
Notes: Zn ion for catalytic activity, Hg ion for structural stability of the ArM, kcat/KM ≈ 1.8*105 M-1*s-1. PDB ID 3PBJ = Structure of an analogue.

Reconstitution of [Fe]-Hydrogenase Using Model Complexes

Hu, X.; Shima, S.

Nat. Chem. 2015, 7, 995-1002, 10.1038/Nchem.2382

[Fe]-Hydrogenase catalyses the reversible hydrogenation of a methenyltetrahydromethanopterin substrate, which is an intermediate step during the methanogenesis from CO2 and H2. The active site contains an iron-guanylylpyridinol cofactor, in which Fe2+ is coordinated by two CO ligands, as well as an acyl carbon atom and a pyridinyl nitrogen atom from a 3,4,5,6-substituted 2-pyridinol ligand. However, the mechanism of H2 activation by [Fe]-hydrogenase is unclear. Here we report the reconstitution of [Fe]-hydrogenase from an apoenzyme using two FeGP cofactor mimics to create semisynthetic enzymes. The small-molecule mimics reproduce the ligand environment of the active site, but are inactive towards H2 binding and activation on their own. We show that reconstituting the enzyme using a mimic that contains a 2-hydroxypyridine group restores activity, whereas an analogous enzyme with a 2-methoxypyridine complex was essentially inactive. These findings, together with density functional theory computations, support a mechanism in which the 2-hydroxy group is deprotonated before it serves as an internal base for heterolytic H2 cleavage.


Metal: Fe
Ligand type: Amino acid
Anchoring strategy: Covalent
Optimization: Chemical
Max TON: ---
ee: ---
PDB: ---
Notes: DFT calculations of the reaction mechanism.

Synthetic Cascades are Enabled by Combining Biocatalysts with Artificial Metalloenzymes

Turner, N.J.; Ward, T.R.

Nat. Chem. 2013, 5, 93-99, 10.1038/NCHEM.1498

Enzymatic catalysis and homogeneous catalysis offer complementary means to address synthetic challenges, both in chemistry and in biology. Despite its attractiveness, the implementation of concurrent cascade reactions that combine an organometallic catalyst with an enzyme has proven challenging because of the mutual inactivation of both catalysts. To address this, we show that incorporation of a d6-piano stool complex within a host protein affords an artificial transfer hydrogenase (ATHase) that is fully compatible with and complementary to natural enzymes, thus enabling efficient concurrent tandem catalysis. To illustrate the generality of the approach, the ATHase was combined with various NADH-, FAD- and haem-dependent enzymes, resulting in orthogonal redox cascades. Up to three enzymes were integrated in the cascade and combined with the ATHase with a view to achieving (i) a double stereoselective amine deracemization, (ii) a horseradish peroxidase-coupled readout of the transfer hydrogenase activity towards its genetic optimization, (iii) the formation of L-pipecolic acid from L-lysine and (iv) regeneration of NADH to promote a monooxygenase-catalysed oxyfunctionalization reaction.


Metal: Ir
Ligand type: Amino-sulfonamide; Cp*
Host protein: Streptavidin (Sav)
Anchoring strategy: Supramolecular
Optimization: Genetic
Max TON: 100
ee: > 99
PDB: ---
Notes: Cascade