1DFM:
reference: Understanding the immutability of restriction enzymes: crystal structure of BglII and its DNA substrate at 1.5 A resolution., Lukacs CM, Kucera R, Schildkraut I, Aggarwal AK, Nat Struct Biol 2000 Feb;7(2):134-40. PMID: 10655616

This OCA Structure page
uses Jmol, developed by the Jmol Development Team (documentation).