Figure 3.

Canonical mechanism of Holliday junction resolution. (A) Antiparallel stacked-X Holliday junction with twofold symmetry. (B) Canonical Holliday junction resolvases are dimeric enzymes that induce structural changes to the junction on binding, causing the junction to unfold. Resolution occurs by the introduction of two coordinated and symmetrically related nicks in strands of like polarity at, or very near, the branchpoint. (C) Symmetrical resolution gives a pair of nicked DNA duplexes, each of which can be directly repaired by nick ligation. Asterisks signify a given strand of DNA. (From West 2009; adapted, with permission, from the author.)