A Novel Mechanism for Pyrimidine Methylation by a Flavin-dependent Enzyme

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With this award, the Chemistry of Life Processes program is supporting the research of Professor Bruce Palfey of the University of Michigan to study the reaction mechanism of the flavin dependent thymidylate synthase. All life requires thymidylate in order to synthesize DNA. The "classic" thymidylate synthase, studied in high detail for half a century, transfers carbon from methylenetetrahydrofolate to deoxyuridine monophosphate through a series of covalent intermediates. It does this without a prosthetic group. In contrast, flavin-dependent thymidylate synthase, discovered just a decade ago, accomplishes the same net transfer of carbon, but somehow the flavin prosthetic group is critical to the process. The reactions that reduce and oxidize the flavin prosthetic group and transfer carbon from methylenetetrahydrofolate will be examined by several spectroscopic and kinetic methods, in the hope of identifying intermediates and understanding how the protein controls the reactions. The novel possibility will be explored that flavin-dependent thymidylate synthase activates deoxyuridine monophosphate by polarization instead of attack by an enzymic nucleophile.The Broader Impacts of this project include insight on the mechanistic and evolutionary malleability of chemical routes critical to life. The flavin-dependent thymidylate synthase reaction is just one example of the widespread reactions that methylate the pyrimidines of nucleic acids or their precursors. For the students involved, this project is expected to provide multi-disciplinary training, including molecular biology, protein biochemistry, spectroscopy, kinetics and organic synthesis. The investigator plans to recruit underprivileged high school students into the laboratory via participation in the American Chemical Society's Project SEED.This project is being co-funded by the Biomolecular Dynamics, Structure and Function Cluster in the Molecular and Cellular Biosciences Division of the BIO Directorate.