Crystallization and preliminary X-ray study of Pk-REC from a hyperthermophilic archaeon, Pyrococcus kodakaraensis KOD1

Pk-REC is a protein which binds to DNA and catalyzes the central step of re combination and repair. The protein was crystallized using the hanging-drop vapour-diffusion method with PEG as a precipitant. Two orthorhombic crysta l forms I and II with the same space group P2(1)2(1)2(1) were obtained at p H 8.0 using PEG 3000 and PEG 550 monomethylether, respectively. The unit-ce ll parameters were a = 151, b = 174, c = 241 Angstrom for form I and a = 15 1, b = 176, c = 300 Angstrom for form II, indicating that the asymmetric un it contains more than 20 molecules.