Stable and Promiscuous Galactose Oxidases Engineered by Directed Evolution, Atomistic Design, and Ancestral Sequence Reconstruction.

Galactose oxidase (GOase) is a versatile biocatalyst with a wide range of potential applications, ranging from synthetic chemistry to bioelectrochemical devices. Previous GOase engineering by directed evolution generated the M-RQW mutant, with unprecedented new-to-nature oxidation activity at the C6-OH group of glucose, and a mutational backbone that helped to unlock its promiscuity toward other molecules, including secondary alcohols. In the current study, we have used the M-RQW mutant as a starting point to engineer a set of GOases that are very thermostable and that are easily produced at high titers in yeast, enzymes with latent activities applicable to sustainable chemistry.

Directed evolution of the multicopper oxidase laccase for cell surface proximity labeling and electron microscopy.

Enzymes that oxidize aromatic substrates have shown utility in a range of cell-based technologies including live cell proximity labeling (PL) and electron microscopy (EM), but are associated with drawbacks such as the need for toxic HO. Here, we explore laccases as a novel enzyme class for PL and EM in mammalian cells. LaccID, generated via 11 rounds of directed evolution from an ancestral fungal laccase, catalyzes the one-electron oxidation of diverse aromatic substrates using O instead of toxic HO, and exhibits activity selective to the surface plasma membrane of both living and fixed cells.

Engineering synthetic agonists for targeted activation of Notch signaling.

Notch signaling regulates cell fate decisions and has context-dependent tumorigenic or tumor suppressor functions. Although there are several classes of Notch inhibitors, the mechanical force requirement for Notch receptor activation has hindered attempts to generate soluble agonists. To address this problem, we engineered synthetic Notch agonist (SNAG) proteins by tethering affinity-matured Notch ligands to antibodies or cytokines that internalize their targets.

Lineage-tracing hematopoietic stem cell origins in vivo to efficiently make human HLF+ HOXA+ hematopoietic progenitors from pluripotent stem cells.

The developmental origin of blood-forming hematopoietic stem cells (HSCs) is a longstanding question. Here, our non-invasive genetic lineage tracing in mouse embryos pinpoints that artery endothelial cells generate HSCs. Arteries are transiently competent to generate HSCs for 2.

The colors of peroxygenase activity: Colorimetric high-throughput screening assays for directed evolution.

Fungal unspecific peroxygenases (UPOs) are arising as versatile biocatalysts for C-H oxyfunctionalization reactions. In recent years, several directed evolution studies have been conducted to design improved UPO variants. An essential part of this protein engineering strategy is the design of reliable colorimetric high-throughput screening (HTS) assays for mutant library exploration.

Engineering a Highly Regioselective Fungal Peroxygenase for the Synthesis of Hydroxy Fatty Acids.

The hydroxylation of fatty acids is an appealing reaction in synthetic chemistry, although the lack of selective catalysts hampers its industrial implementation. In this study, we have engineered a highly regioselective fungal peroxygenase for the ω-1 hydroxylation of fatty acids with quenched stepwise over-oxidation. One single mutation near the Phe catalytic tripod narrowed the heme cavity, promoting a dramatic shift toward subterminal hydroxylation with a drop in the over-oxidation activity.

Affinity-matured DLL4 ligands as broad-spectrum modulators of Notch signaling.

The Notch pathway regulates cell fate decisions and is an emerging target for regenerative and cancer therapies. Recombinant Notch ligands are attractive candidates for modulating Notch signaling; however, their intrinsically low receptor-binding affinity restricts their utility in biomedical applications. To overcome this limitation, we evolved variants of the ligand Delta-like 4 with enhanced affinity and cross-reactivity.

Fucosylated Proteome Profiling Identifies a Fucosylated, Non-Ribosomal, Stress-Responsive Species of Ribosomal Protein S3.

Alterations in genes encoding for proteins that control fucosylation are known to play causative roles in several developmental disorders, such as Dowling-Degos disease 2 and congenital disorder of glycosylation type IIc (CDGIIc). Recent studies have provided evidence that changes in fucosylation can contribute to the development and progression of several different types of cancers. It is therefore important to gain a detailed understanding of how fucosylation is altered in disease states so that interventions may be developed for therapeutic purposes.

Random and combinatorial mutagenesis for improved total production of secretory target protein in Escherichia coli.

Signal peptides and secretory carrier proteins are commonly used to secrete heterologous recombinant protein in Gram-negative bacteria. The Escherichia coli osmotically-inducible protein Y (OsmY) is a carrier protein that secretes a target protein extracellularly, and we have previously applied it in the Bacterial Extracellular Protein Secretion System (BENNY) to accelerate directed evolution. In this study, we reported the first application of random and combinatorial mutagenesis on a carrier protein to enhance total secretory target protein production.

Accelerated directed evolution of dye-decolorizing peroxidase using a bacterial extracellular protein secretion system (BENNY).

Background: Dye-decolorizing peroxidases (DyPs) are haem-containing peroxidases that show great promises in industrial biocatalysis and lignocellulosic degradation. Through the use of osmotically-inducible protein Y (OsmY) as a bacterial extracellular protein secretion system (BENNY), we successfully developed a streamlined directed evolution workflow to accelerate the protein engineering of DyP4 from strain PC15.

Result: After 3 rounds of random mutagenesis with error-prone polymerase chain reaction (epPCR) and 1 round of saturation mutagenesis, we obtained 4D4 variant (I56V, K109R, N227S and N312S) that displays multiple desirable phenotypes, including higher protein yield and secretion, higher specific activity (2.

Molecular engineering strategies for visualizing low-affinity protein complexes.

Unlabelled: The growing availability of complex structures in the Protein Data Bank has provided key insight into the molecular architecture of protein–protein interfaces. The remarkable diversity observed in protein binding modes is paralleled by a tremendous variation in binding affinities, with interaction half-lives ranging from days to milliseconds. Within the protein interactome, low-affinity binding events have been particularly difficult to visualize by traditional structural methods, which has spurred the development of innovative strategies for reconstituting these short-lived yet biologically essential assemblies.

Directed Evolution Method in Saccharomyces cerevisiae: Mutant Library Creation and Screening.

Directed evolution in Saccharomyces cerevisiae offers many attractive advantages when designing enzymes for biotechnological applications, a process that involves the construction, cloning and expression of mutant libraries, coupled to high frequency homologous DNA recombination in vivo. Here, we present a protocol to create and screen mutant libraries in yeast based on the example of a fungal aryl-alcohol oxidase (AAO) to enhance its total activity. Two protein segments were subjected to focused-directed evolution by random mutagenesis and in vivo DNA recombination.

Focused Directed Evolution of Aryl-Alcohol Oxidase in Saccharomyces cerevisiae by Using Chimeric Signal Peptides.

Aryl-alcohol oxidase (AAO) is an extracellular flavoprotein that supplies ligninolytic peroxidases with H2O2 during natural wood decay. With a broad substrate specificity and highly stereoselective reaction mechanism, AAO is an attractive candidate for studies into organic synthesis and synthetic biology, and yet the lack of suitable heterologous expression systems has precluded its engineering by directed evolution. In this study, the native signal sequence of AAO from Pleurotus eryngii was replaced by those of the mating α-factor and the K1 killer toxin, as well as different chimeras of both prepro-leaders in order to drive secretion in Saccharomyces cerevisiae.

Assembly of evolved ligninolytic genes in Saccharomyces cerevisiae.

The ligninolytic enzymatic consortium produced by white-rot fungi is one of the most efficient oxidative systems found in nature, with many potential applications that range from the production of 2nd generation biofuels to chemicals synthesis. In the current study, two high redox potential oxidoreductase fusion genes (laccase -Lac- and versatile peroxidase -Vp-) that had been evolved in the laboratory were re-assembled in Saccharomyces cerevisiae. First, cell viability and secretion were assessed after co-transforming the Lac and Vp genes into yeast.

Directed evolution of unspecific peroxygenase from Agrocybe aegerita.

Unspecific peroxygenase (UPO) represents a new type of heme-thiolate enzyme with self-sufficient mono(per)oxygenase activity and many potential applications in organic synthesis. With a view to taking advantage of these properties, we subjected the Agrocybe aegerita UPO1-encoding gene to directed evolution in Saccharomyces cerevisiae. To promote functional expression, several different signal peptides were fused to the mature protein, and the resulting products were tested.

Mutagenic Organized Recombination Process by Homologous IN vivo Grouping (MORPHING) for directed enzyme evolution.

Approaches that depend on directed evolution require reliable methods to generate DNA diversity so that mutant libraries can focus on specific target regions. We took advantage of the high frequency of homologous DNA recombination in Saccharomyces cerevisiae to develop a strategy for domain mutagenesis aimed at introducing and in vivo recombining random mutations in defined segments of DNA. Mutagenic Organized Recombination Process by Homologous IN vivo Grouping (MORPHING) is a one-pot random mutagenic method for short protein regions that harnesses the in vivo recombination apparatus of yeast.

Functional expression of a blood tolerant laccase in Pichia pastoris.

Background: Basidiomycete high-redox potential laccases (HRPLs) working in human physiological fluids (pH 7.4, 150 mM NaCl) arise great interest in the engineering of 3D-nanobiodevices for biomedical uses. In two previous reports, we described the directed evolution of a HRPL from basidiomycete PM1 strain CECT 2971: i) to be expressed in an active, soluble and stable form in Saccharomyces cerevisiae, and ii) to be active in human blood.

Blood tolerant laccase by directed evolution.

High-redox potential laccases are powerful biocatalysts with a wide range of applications in biotechnology. We have converted a thermostable laccase from a white-rot fungus into a blood tolerant laccase. Adapting the fitness of this laccase to the specific composition of human blood (above neutral pH, high chloride concentration) required several generations of directed evolution in a surrogate complex blood medium.

Saccharomyces cerevisiae in directed evolution: An efficient tool to improve enzymes.

Over the past 20 years, directed evolution has been seen to be the most reliable approach to protein engineering. Emulating the natural selection algorithm, ad hoc enzymes with novel features can be tailor-made for practical purposes through iterative rounds of random mutagenesis, DNA recombination and screening. Of the heterologous hosts used in laboratory evolution experiments, the budding yeast Saccharomyces cerevisiae has become the best choice to express eukaryotic proteins with improved properties.

Structural and kinetic insights reveal that the amino acid pair Gln-228/Asn-254 modulates the transfructosylating specificity of Schwanniomyces occidentalis β-fructofuranosidase, an enzyme that produces prebiotics.

Schwanniomyces occidentalis β-fructofuranosidase (Ffase) is a GH32 dimeric enzyme that releases fructose from the nonreducing end of various oligosaccharides and essential storage fructans such as inulin. It also catalyzes the transfer of a fructosyl unit to an acceptor producing 6-kestose and 1-kestose, prebiotics that stimulate the growth of bacteria beneficial for human health. We report here the crystal structure of inactivated Ffase complexed with fructosylnystose and inulin, which shows the intricate net of interactions keeping the substrate tightly bound at the active site.

Directed evolution of a temperature-, peroxide- and alkaline pH-tolerant versatile peroxidase.

The VPs (versatile peroxidases) secreted by white-rot fungi are involved in the natural decay of lignin. In the present study, a fusion gene containing the VP from Pleurotus eryngii was subjected to six rounds of directed evolution, achieving a level of secretion in Saccharomyces cerevisiae (21 mg/l) as yet unseen for any ligninolytic peroxidase. The evolved variant for expression harboured four mutations and increased its total VP activity 129-fold.