Preliminary time-of-flight neutron diffraction study on diisopropyl fluorophosphatase (DFPase) from Loligo vulgaris.

Marc-Michael Blum, Alexander Koglin, Heinz Rüterjans, Benno Schoenborn, Paul Langan, Julian C-H Chen

Index: Acta Crystallogr. Sect. F Struct. Biol. Cryst. Commun. 63(Pt 1) , 42-5, (2007)

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Abstract

The enzyme diisopropyl fluorophosphatase (DFPase) from Loligo vulgaris is capable of decontaminating a wide variety of toxic organophosphorus nerve agents. DFPase is structurally related to a number of enzymes, such as the medically important paraoxonase (PON). In order to investigate the reaction mechanism of this phosphotriesterase and to elucidate the protonation state of the active-site residues, large-sized crystals of DFPase have been prepared for neutron diffraction studies. Available H atoms have been exchanged through vapour diffusion against D2O-containing mother liquor in the capillary. A neutron data set has been collected to 2.2 A resolution on a relatively small (0.43 mm3) crystal at the spallation source in Los Alamos. The sample size and asymmetric unit requirements for the feasibility of neutron diffraction studies are summarized.