Purified protein was concentrated to 10 mg/ml in 20 mM Tris-HCl (pH 8.0) and 50 mM NaCl. Crystals with quality diffraction were obtained using the hanging drop vapor diffusion after 2 weeks at 4uC by mixing 2 ml of the protein with 2 ml of the reservoir solution containing 2.1 M ammonium sulfate and 6% v/v iso-propanol. Prior to data collection, crystals were transferred to the mother liquor containing 30% (v/v) glycerol as cryoprotectant and flash frozen in liquid nitrogen. X-ray Data were collected using a Rigaku MicroMax007 rotating-anode Xray generator equipped with an R-AXIS IV image-plate detector. Data were processed and scaled using MOSFLM [59] and SCALA [60] .