Crystallization and preliminary X-ray crystallographic analysis of DFPase from Loligo vulgaris

'Squid-type' diisopropylfluorophosphatases (DFPases), a subclass of the pho sphotriesterases, are enzymes capable of hydrolysing organophosphorus nerve agents. To date, no three-dimensional structure of a 'squid-type' DFPase i s known. Here, the crystallization of the DFPase originally isolated from h ead ganglion of the squid Loligo vulgaris is reported. The protein has been heterologously expressed in Escherichia coli, purified to homogeneity and subsequently crystallized. The protein crystals belong to space group P2(1) 2(1)2(1), with unit-cell parameters a = 43.1, b = 82.1, c = 86.6 Angstrom a nd one monomer per asymmetric unit. Under cryoconditions (120 K) the crysta ls diffracted beyond 2.0 Angstrom using a Cu rotating-anode X-ray generator .