Crystallization and preliminary X‐ray analysis of a RecB‐family nuclease from the archaeon Pyrococcus abyssi

Nucleases are required to process and repair DNA damage in living cells. One of the best studied nucleases is the RecB protein, which functions in Escherichia coli as a component of the RecBCD enzyme complex that amends double‐strand breaks in DNA. Although archaea do not contain the RecBCD complex, a RecB‐like nuclease from Pyrococcus abyssi has been cloned, expressed and purified. The protein was crystallized by the sitting‐drop vapour‐diffusion method using polyethylene glycol 8000 as the precipitant. The crystals belong to the orthorhombic space group C 222 1 , with unit‐cell parameters a = 81.5, b  = 159.8, c = 100.8 Å. Self‐rotation function and native Patterson map calculations revealed that there is a dimer in the asymmetric unit with its local twofold axis running parallel to the crystallographic twofold screw axis. The crystals diffracted to about 2 Å and a complete native data set was collected to 2.65 Å resolution.