Abstract
BackgroundA 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 FindingsHere, 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/SignificanceWe 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.
Highlights
SisLac is an enzyme isolated from the archaeon organism Sulfolobus islandicus, which is found in extreme environments like the Yellowstone natural park (U.S.A.) or the Mutnovksy volcano in Kamchatka (Russia) [2]
Some representatives of Phosphotriesterase-Like Lactonases (PLL) were primarily isolated by virtue of their phosphotriesterase activity towards the insecticide paraoxon, and were named paraoxonases (Pox) as was the case with SisLac’s closest homologue, SsoPox, an enzyme isolated from Sulfolobus solfataricus [6]
This study provides the characterization of SisLac isolated from Sulfolobus islandicus strain M.16.4
Summary
SisLac ( known as SisPox [1]) is an enzyme isolated from the archaeon organism Sulfolobus islandicus, which is found in extreme environments like the Yellowstone natural park (U.S.A.) or the Mutnovksy volcano in Kamchatka (Russia) [2]. SisLac belongs to an enzyme family called Phosphotriesterase-Like Lactonase (PLL) that encompasses members from mesophilic organisms (PPH, AhlA, MCP, DrOPH) [3,4,5] as well as thermophilic (SsoPox, SacPox, GsP, GkL) [6,7,8,9] representatives. Some representatives of PLLs were primarily isolated by virtue of their phosphotriesterase activity towards the insecticide paraoxon, and were named paraoxonases (Pox) as was the case with SisLac’s closest homologue, SsoPox, an enzyme isolated from Sulfolobus solfataricus [6]. 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 represents a promising target for engineering studies, exhibiting both detoxification and bacterial quorum quenching abilities, including human pathogens such as Pseudomonas aeruginosa
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