Sau3AI, a Monomeric Type II Restriction Endonuclease That Dimerizes on the DNA and Thereby Induces DNA Loops

• DOI: 10.1074/jbc.m101694200
• Publication Date: 2002-07-26T15:16:07Z
• Authors: Peter Friedhoff; Rudi Lurz; Gerhild Lüder; Alfred Pingoud
• Keywords: Cleavage (geology)

Here, we report that <i>Sau</i>3AI, an unusually large type II restriction enzyme with sequence homology to the mismatch repair protein MutH, is a monomeric as shown by gel filtration and ultracentrifugation. Structural similarities in N- C-terminal halves of suggest <i>Sau</i>3AI pseudo-dimer, <i>i.e.</i> polypeptide two similar domains. Since displays nonlinear dependence cleavage activity on concentration strong preference for substrates recognition sites over those only one, it likely functionally active form dimer pseudo-dimer. Indeed, electron microscopy studies demonstrate distant are brought together through DNA looping induced simultaneous binding two<i>Sau</i>3AI molecules DNA. We dimeric supplies DNA-binding sites, one associated catalytic center serves effector site.