Crystallization and preliminary X-ray analysis of restriction endonuclease BamHI-DNA complex

Restriction endonuclease BamHI from Bacillus amyloliquefaciens has been co-crystallized with a 12 bp DNA fragment that encompasses its recognition site. The co-crystals diffract to at least 1.95 Å resolution and belong to space group P2₁2₁2₁. The unit cell parameters are a = 108.8 Å, b = 81.9 Å, c = 68.8 Å consistent with one complex in the crystallographic asymmetric unit. The direction of the DNA appears to be along the b axis. In order to achieve end to end stacking of DNA, the complex must lie on the screw axis along b. A selfrotation function has determined the directions of the non-crystallographic 2-fold axes.