3.6.1.66 crystals are grown by hanging-drop vapor diffusion method, the crystal structure of the protein is determined at 2.2 A resolution 728362 3.6.1.66 oil microbatch method. High resolution crystal structures of the enzyme in two unliganded forms and in three liganded forms with the substrate ITP, the product IMP and the divalent cation Mn2+ are determined. Based on these structures, a mechanism of the divalent cation-dependent ITP hydrolysis is proposed 745548 3.6.1.66 protein X-ray structure of the enzyme with bound IMP is obtained at 2.15 A resolution and compare it with structures of unliganded TM0159 and other noncanonical NTPases 746613