Crystallization and preliminary X-ray diffraction analysis of homing endonuclease I-Tsp061I

Two crystal forms, rhombohedral and hexagonal, of a homing endonuclease from Thermoproteus sp. IC-061 (I-Tsp0611) were obtained by the hanging-drop and sitting-drop method, respectively. The hexagonal crystals belong to space group P6(3)22, with unit-cell parameters a = b = 111.4, c = 97.6 A, and diffract to 3.2 A resolution on beamline BL44 at SPring-8 (Harima, Japan). The rhombohedral crystals belong to space group R32, with unit-cell parameters a = b = 95.4, c = 192.9 A, and diffract to 2.7 A resolution using a Cu Kalpha rotating-anode generator with an R-AXIS VII detector. The crystal asymmetric unit contained one protein molecule and the solvent contents of the two crystal forms were estimated to be 68.3 and 67.6% by volume, respectively.