Catalytic Mechanism and Structure of Viral Flavin-Dependent Thymidylate Synthase Thyx.Graziani, S., Bernauer, J., Skouloubris, S., Graille, M., Zhou, C.-Z., Marchand, C., Decottignies, P., Van Tilbeurgh, H., Myllykallio, H., Liebl, U.
(2006) J Biol Chem 281: 24048
- PubMed: 16707489
- DOI: https://doi.org/10.1074/jbc.M600745200
- Primary Citation of Related Structures:
- PubMed Abstract:
By using biochemical and structural analyses, we have investigated the catalytic mechanism of the recently discovered flavin-dependent thymidylate synthase ThyX from Paramecium bursaria chlorella virus-1 (PBCV-1). Site-directed mutagenesis experiments have identified several residues implicated in either NADPH oxidation or deprotonation activity of PBCV-1 ThyX. Chemical modification by diethyl pyrocarbonate and mass spectroscopic analyses identified a histidine residue (His53) crucial for NADPH oxidation and located in the vicinity of the redox active N-5 atom of the FAD ring system. Moreover, we observed that the conformation of active site key residues of PBCV-1 ThyX differs from earlier reported ThyX structures, suggesting structural changes during catalysis. Steady-state kinetic analyses support a reaction mechanism where ThyX catalysis proceeds via formation of distinct ternary complexes without formation of a methyl enzyme intermediate.
CNRS, UMR 7645, Laboratory of Optics and Biosciences, Ecole Polytechnique, 91128 Palaiseau, France.