Functional evidence for active site location of tetrameric thymidylate synthase X at the interphase of three monomers

Damien Leduc (1) , Sébastien Graziani (2) , Gérard Lipowski (2) , C. Marchand (3) , P. Le Maréchal (3) , Ursula Liebl (2) , Hannu Myllykallio (1)

1 IGM - Institut de génétique et microbiologie [Orsay]
2 LOB - Laboratoire d'optique et biosciences
3 IBBMC - Institut de biochimie et biophysique moléculaire et cellulaire

Little is known about the catalytic mechanism of the recently discovered ThyX family of flavin-dependent thymidylate synthases that are required for thymidylate (deoxythymidine 5'-monophosphate) synthesis in a large number of microbial species. Using a combination of site-directed mutagenesis and biochemical measurements, we have identified several residues of the Helicobacter pylori ThyX protein with crucial roles in ThyX catalysis. By providing functional evidence that the active site(s) of homotetrameric ThyX proteins is formed by three different subunits, our findings suggest that ThyX proteins have evolved through multimerization of inactive monomers. Moreover, because the active-site configurations of ThyX proteins, present in many human pathogenic bacteria, and of human thymidylate synthase ThyA are different, our results will aid in the identification of compounds specifically inhibiting microbial growth.

Damien Leduc, Sébastien Graziani, Gérard Lipowski, C. Marchand, P. Le Maréchal, et al.. Functional evidence for active site location of tetrameric thymidylate synthase X at the interphase of three monomers. Proceedings of the National Academy of Sciences of the United States of America, 2004, 101 (19), pp.7252-7257. ⟨10.1073/pnas.0401365101⟩. ⟨hal-00831844⟩