Organophosphates are the largest class of known insecticides, several of which are potent nerve agents. Consequently, organophosphate-degrading enzymes are of great scientific interest as bioscavengers and biodecontaminants. Recently, a hyperthermophilic phosphotriesterase (known as SsoPox), from the Archaeon Sulfolobus solfataricus, has been isolated and found to possess a very high lactonase activity. Here, we report the three-dimensional structures of SsoPox in the apo form (2.6 Å resolution) and in complex with a quorum-sensing lactone mimic at 2.0 Å resolution. The structure also reveals an unexpected active site topology, and a unique hydrophobic channel that perfectly accommodates the lactone substrate. Structural and mutagenesis evidence allows us to propose a mechanism for lactone hydrolysis and to refine the catalytic mechanism established for phosphotriesterases. In addition, SsoPox structures permit the correlation of experimental lactonase and phosphotriesterase activities and this strongly suggests lactonase activity as the cognate function of SsoPox. This example demonstrates that promiscuous activities probably constitute a large and efficient reservoir for the creation of novel catalytic activities.
|Original language||English (US)|
|Number of pages||12|
|Journal||Journal of Molecular Biology|
|State||Published - Jun 20 2008|
Bibliographical noteFunding Information:
We are very grateful to Drs Dan S. Tawfik and Olga Khersonsky for providing the substrate TBBL and C10 HTL inhibitor. This research was supported by grants to P.M. and E.C. by the Délégation Générale pour l'Armement (CO n°010807/03-10) and by the C.N.R.S. We thank the MIUR project Piano Nazionale Ricerca per le Biotecnologie Avanzate II –Biocatalisi and the DNA Sequencing Core of TIGEM-IGB for sequencing mutants.
- 3D structure
- active-site mutants
- hyperthermophilic enzymes