Crystals for Chimera 7 were grown by sitting drop vapor diffusion at 4 ºC using 12 mg/mL protein. The crystallization drop was prepared by mixing 2 μL of protein solution, 0.5 μL sucrose 30 % (w/v) and 3 μL of precipitant solution (0.1 M HEPES pH 7.5, 0.2 M magnesium acetate and 15-20 % polyethylene glycol 8000). Single crystals were visible after three days. Cryoprotection was performed by transferring crystals stepwise into stabilization solution with increasing glycerol amounts to a final concentration of 15% and the respective initial concentrations of ligands present in the protein and precipitant solutions, and then flash-cooled in liquid nitrogen.