Structural and enzymatic characterization of the lactonase SisLac from Sulfolobus islandicus

PLoS One. 2012;7(10):e47028. doi: 10.1371/journal.pone.0047028. Epub 2012 Oct 10.


Background: A new member of the Phosphotriesterase-Like Lactonases (PLL) family from the hyperthermophilic archeon Sulfolobus islandicus (SisLac) has been characterized. SisLac is a native lactonase that exhibits a high promiscuous phosphotriesterase activity. SisLac thus represents a promising target for engineering studies, exhibiting both detoxification and bacterial quorum quenching abilities, including human pathogens such as Pseudomonas aeruginosa.

Methodology/principal findings: Here, we describe the substrate specificity of SisLac, providing extensive kinetic studies performed with various phosphotriesters, esters, N-acyl-homoserine lactones (AHLs) and other lactones as substrates. Moreover, we solved the X-ray structure of SisLac and structural comparisons with the closely related SsoPox structure highlighted differences in the surface salt bridge network and the dimerization interface. SisLac and SsoPox being close homologues (91% sequence identity), we undertook a mutational study to decipher these structural differences and their putative consequences on the stability and the catalytic properties of these proteins.

Conclusions/significance: We show that SisLac is a very proficient lactonase against aroma lactones and AHLs as substrates. Hence, data herein emphasize the potential role of SisLac as quorum quenching agent in Sulfolobus. Moreover, despite the very high sequence homology with SsoPox, we highlight key epistatic substitutions that influence the enzyme stability and activity.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acyl-Butyrolactones
  • Amino Acid Sequence
  • Crystallography, X-Ray
  • Enzyme Stability
  • Esterases / chemistry*
  • Esterases / genetics
  • Esterases / metabolism*
  • Hydrogen-Ion Concentration
  • Kinetics
  • Models, Molecular
  • Molecular Sequence Data
  • Phosphoric Triester Hydrolases / metabolism
  • Protein Conformation
  • Protein Multimerization
  • Quorum Sensing
  • Sequence Homology, Amino Acid
  • Substrate Specificity
  • Sulfolobus / enzymology*
  • Sulfolobus / genetics
  • Temperature


  • Acyl-Butyrolactones
  • Esterases
  • Phosphoric Triester Hydrolases

Associated data

  • PDB/4G2D

Grants and funding

This work was granted by Direction Generale de l’armement (D.G.A.), France (REI. 2009 34 0045) and Vaincre La Mucoviscidose, France. J.H. and G.G. are PhD students granted by D.G.A. M.E. is a fellow supported by the IEF Marie Curie program (grant No. 252836). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.