Structure and function of restriction endonucleases

Structures of two restriction endonucleases, BamHI and PvuII, were reported in the past year. This doubles the number of restriction endonuclease structures now known from two to four, and enables a comparative analysis of their structures and modes DNA recognition. Despite a lack of sequence homology between the enzymes, BamHI turns out to resemble EcoRI, and PvuII turns out to resemble EcoRV. The active-site regions are structurally similar in all four enzymes, but their mechanisms of cleavage may differ.