Elias Mikael, Dupuy Jérôme, Merone Luigia, Mandrich Luigi, Porzio Elena, Moniot Sébastien, Rochu Daniel, Lecomte Claude, Rossi Mosè, Masson Patrick, Manco Giuseppe, Chabriere Eric
Laboratoire de Cristallographie et Modélisation des Matériaux Minéraux et Biologiques, CNRS-Université Henri Poincaré, 54506 Nancy, France.
J Mol Biol. 2008 Jun 20;379(5):1017-28. doi: 10.1016/j.jmb.2008.04.022. Epub 2008 Apr 16.
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 A resolution) and in complex with a quorum-sensing lactone mimic at 2.0 A 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.
有机磷酸酯是已知杀虫剂中最大的一类，其中几种是强效神经毒剂。因此，作为生物清除剂和生物去污剂，有机磷酸酯降解酶具有重大的科学研究价值。最近，从嗜热栖热放线菌中分离出一种嗜热磷酸三酯酶（称为SsoPox），发现它具有非常高的内酯酶活性。在此，我们报告了无配体形式的SsoPox的三维结构（分辨率为2.6埃）以及与群体感应内酯模拟物复合物的三维结构（分辨率为2.0埃）。该结构还揭示了一个意想不到的活性位点拓扑结构，以及一个完美容纳内酯底物的独特疏水通道。结构和诱变证据使我们能够提出内酯水解的机制，并完善为磷酸三酯酶建立的催化机制。此外，SsoPox的结构允许将实验性内酯酶和磷酸三酯酶活性进行关联，这有力地表明内酯酶活性是SsoPox的同源功能。这个例子表明，混杂活性可能构成了创造新催化活性的一个庞大而有效的来源。
