Structure of Fok I has implications for DNA cleavage

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Abstract
Fok I is a member an unusual class of restriction enzymes that recognize a specific DNA sequence and cleave nonspecifically a short distance away from that sequence. Fok I consists of an N-terminal DNA recognition domain and a C-terminal cleavage domain. The bipartite nature of Fok I has led to the development of artificial enzymes with novel specificities. We have solved the structure of Fok I to 2.3 Å resolution. The structure reveals a dimer, in which the dimerization interface is mediated by the cleavage domain. Each monomer has an overall conformation similar to that found in the Fok I–DNA complex, with the cleavage domain packing alongside the DNA recognition domain. In corroboration with the cleavage data presented in the accompanying paper in this issue of Proceedings , we propose a model for Fok I DNA cleavage that requires the dimerization of Fok I on DNA to cleave both DNA strands.