3.1.99.B2 crystal structure of the homodimeric enzyme alone and bound to 15-mer dsDNA 3.1.99.B2 three different crystal forms of the enzyme are grown in trigonal, monoclinic and triclinic systems. The trigonal crystals diffract to 2.8 A and are grown in the presence of double-stranded DNA. Monoclinic crystals are grown without DNA and diffract to 3.2 A