Crystallization and preliminary crystallographic analysis of Bacillus thuringiensis AHL-lactonase

The quorum sensing (QS) systems in Gram-negative bacteria are mostly associated with diffusible N-acyl-L-homoserine lactones (AHLs). AHL-degrading enzymes hydrolyze the AHLs into inactive molecules, thereby blocking the QS systems that are closely linked to virulence factor production and biofilm formation. Consequently, these enzymes have recently attracted intense interest for the development of anti-infection therapies for plants and animals. However, despite significant progress in the investigation of AHL-degrading enzymes, no structure is yet available. Accordingly, this study reports on the expression and purification of the AHL-lactonase from Bacillus thuringiensis subsp. kurstaki HD263, as well as the successful crystallization of the enzyme. High-quality native crystals were obtained and a complete data set collected at 2.0 A resolution. The native crystal was found to belong to the space group P2(1)2(1)2(1), with unit cell parameters a=52.7 A, b=55.9 A, and c=74.1 A and one molecule in the asymmetric unit. MAD data were also collected at 2.4 A resolution for a SeMet-substituted crystal.