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Directed Evolution of Novel Artificial Metalloenzyme Platforms for Biocatalysis

Periodic Reporting for period 1 - ArtMetBio (Directed Evolution of Novel Artificial Metalloenzyme Platforms for Biocatalysis)

Reporting period: 2018-05-01 to 2020-04-30

Catalysis is a critical component of biochemistry and modern industry. In both of these fields, the versatility of a coordinated metal ion is frequently key to obtaining the desired catalytic function. In biology, enzymes often recruit metals to catalyze challenging transformations, such as C-H activation, nitrogen fixation, and water splitting. Despite the diversity of these reactions, natural enzymes are limited by the repertoire of bioavailable metals and ligands. In contrast, synthetic chemists can select from a wider variety of metal ions and ligands to create industrial catalysts. Thus, abiological metal catalysts enable reactions not found in nature with high enantioselectivity, versatility, and broad substrate scope. These catalysts, however, are often inferior to enzyme catalysts in terms of turnover number, efficiency, and selectivity. To take advantage of these complementary approaches, artificial metalloenzymes have emerged as a synergistic fusion of synthetic and biological catalysts. These hybrid catalysts have the potential to harness the advantages of both systems, inheriting the versatility of synthetic catalysts and the efficiency and robustness of enzymes. The objective of the ArtMetBio project is to create novel platforms for artificial metalloenzymes that optimize catalytic performance and versatility via increased cooperation between the synthetic and biological components.
Throughout this work, the researcher was able to express two distinct proteins to serve as novel scaffolds for ArMs. Twelve catalytic cofactors were synthesized for the creation of ArMs. These twelve cofactors include catalysts for metathesis, deallylation, and transfer hydrogenation. Each cofactor was screened for efficient binding to the desired scaffold protein. Those cofactors that bound to the scaffold rapidly were screened for activity in the presence and absence of the scaffold protein. Directed evolution was carried out for the best metathesis cofactors and a wild-type scaffold protein. Directed evolution produced only modest increases in catalytic activity of the metathesis ArM. Currently, the researcher is pursuing directed evolution for analogous ArMs for deallylation and transfer hydrogenation.
This work enabled the evaluation of novel scaffold proteins for creating new biocatalysts. Through the course of this work, several methods were developed for the efficient screening and evaluation of biocatalysts in both whole cells and with purified protein. Knowledge transfer was a key aspect in this project. The researcher was able to introduce new DNA library creation methods, new screening methods, and enzymology knowledge to the laboratory. And the laboratory provided the researcher with the opportunity to i) learn new techniques in machine learning, ii) gain invaluable teaching experience, iii) mentor students, and iv) advance the researcher's career goals.
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