Expression, purification and preliminary crystallographic analysis of the Toxoplasma gondii enoyl reductase

The protozoan parasite Toxoplasma gondii is the causative agent of one of the most widespread parasitic infections of man and is a leading cause of congenital neurological birth defects and the third most common cause of food-borne deaths in the United States. Despite this, to date no drugs are available that provide a fully effective treatment. Recently, the antibacterial agent triclosan was shown to inhibit the fatty-acid biosynthesis pathway in T. gondii and to interact with the enoyl reductase (ENR). In order to analyse the potential of triclosan as a lead compound targeting T. gondii ENR and to explore unique features of the apicomplexan enzyme that could be exploited in future drug development, structural studies have been initiated on T. gondii ENR. Crystals of T. gondii ENR in complex with NAD+ and triclosan were grown using the hanging-drop vapour-diffusion method with PEG 8000 as precipitant. The crystals belong to space group P3(2)21, with approximate unit-cell parameters a = 78.1, b = 78.1, c = 188.5 A, alpha = beta = 90, gamma = 120 degrees and a dimer in the asymmetric unit. Test data were collected to beyond 2.6 A on cryocooled crystals (100 K) using a Rigaku MM007 rotating-anode X-ray source, revealing that the crystals are suitable for a full structural determination.