Structural determinants of the high thermal stability of SsoPox from the hyperthermophilic archaeon Sulfolobus solfataricus

Pompea Del Vecchio, Mikael Elias, Luigia Merone, Giuseppe Graziano, Jérôme Dupuy, Luigi Mandrich, Paola Carullo, Bertrand Fournier, Daniel Rochu, Mosè Rossi, Patrick Masson, Eric Chabriere, Giuseppe Manco

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53 Scopus citations


Organophosphates (OPs) constitute the largest class of insecticides used worldwide and certain of them are potent nerve agents. Consequently, enzymes degrading OPs are of paramount interest, as they could be used as bioscavengers and biodecontaminants. Looking for a stable OPs catalyst, able to support industrial process constraints, a hyperthermophilic phosphotriesterase (PTE) (SsoPox) was isolated from the archaeon Sulfolobus solfataricus and was found to be highly thermostable. The solved 3D structure revealed that SsoPox is a noncovalent dimer, with lactonase activity against "quorum sensing signals", and therefore could represent also a potential weapon against certain pathogens. The structural basis of the high thermostability of SsoPox has been investigated by performing a careful comparison between its structure and that of two mesophilic PTEs from Pseudomonas diminuta and Agrobacterium radiobacter. In addition, the conformational stability of SsoPox against the denaturing action of temperature and GuHCl has been determined by means of circular dichroism and fluorescence measurements. The data suggest that the two fundamental differences between SsoPox and the mesophilic counterparts are: (a) a larger number of surface salt bridges, also involved in complex networks; (b) a tighter quaternary structure due to an optimization of the interactions at the interface between the two monomers.

Original languageEnglish (US)
Pages (from-to)461-470
Number of pages10
Issue number3
StatePublished - May 2009

Bibliographical note

Funding Information:
Acknowledgments This research was supported by grants to E.C. by Délégation Générale pour l’Armement (CO no. 010807/03-10) and by the C.N.R.S. D.R. is under contract with Bundesministerium der Verteidigung (M/SAB/1/7/A004). We also thank MIUR project ‘‘Piano Nazionale Ricerca per le Biotecnologie Avanzate Tema II, Biocatalisi’’.


  • Conformational stability
  • Hyperthermophilic enzyme
  • Quaternary structure organization
  • Salt bridges


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