CBS Biochemistry
College of Biological Sciences
Twin Cities
Project Title: 
Structural Enzymology in Natural Product Biosynthesis

Peptide-derived natural products can be generated either via the ribosome or via the action of non-ribosomal peptide synthetases. These make up a vast library of compounds, many of which have therapeutic activities, such as antibiotic, anti-viral, anti-fungal, and anti-cancer. Most peptide-based natural products are too complex to synthesize chemically, and so natural enzymes or bioengineered variants are required to generate the compounds or their derivatives. As such, it is important to define the chemical and structural mechanisms of the enzymes involved in peptide-derived natural product biosynthesis if we are to use or manipulate their product profiles.

Previous work in this lab has focused on post-translational protein modifications that generate in situ redox cofactors within the active sites of enzymes. To study the biosynthesis and chemistry of these unusual cofactors, catalytic reactions were run in enzyme crystals and flash-cooled when an intermediate of interest had built up within the crystal, thus pressing the "pause" button on the reaction. X-ray crystal structures of these trapped catalytic intermediates provided "snapshots" along the reaction coordinate enabling a "movie of catalysis" to be constructed. Single crystal spectroscopies were coupled to the X-ray crystallography to correctly place the structure within the reaction. The resulting structures provided a molecular window into the underlying catalytic chemistry.

Moving forward, the primary research focus of the lab changes from proteins to peptides - specifically the biosynthesis of peptide-derived natural products. The initial focus will be the biosynthesis of pyrroloquinoline quinone, mycofactocin, and β-lactone natural products. X-ray crystallography, NMR, single crystal UV-visible spectroscopy, and in crystallo cryotrapping will be used to interrogate β-lactone synthetases, radical SAM-SPASM enzymes, and a cofactorless oxidase, as well as investigate the role of peptide chaperones. As well as natural product biosynthesis, these studies will shed light on fundamental processes relevant to human health and well-being, such as oxygen activation and radical-based chemistry.

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