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 recombination and repair. The protein was crystallized using the hanging-drop vapour-diffusion method with PEG as a precipitant. Two orthorhombic crystal forms I and II with the same space group P2₁2₁2₁ were obtained at pH 8.0 using PEG 3000 and PEG 550 monomethylether, respectively. The unit-cell parameters were a = 151, b = 174, c = 241 Å for form I and a = 151, b = 176, c = 300 Å for form II, indicating that the asymmetric unit contains more than 20 molecules.