Figure 1 - full size

 

Figure 1.
Fig. 1. Site-specific recombination by resolvase. (A) Two res sites in negatively supercoiled, closed circular DNA bind wild-type resolvase as a dimer (blue and red spheres) at site I in the presynaptic state (dashed-line box). The synaptosome consists of the two res sites, each containing three resolvase dimers bound to sites I, II, and III (left) associating to form an assembly (right). During strand exchange, a synaptic complex at site I (yellow box) is formed by a resolvase tetramer that becomes covalently linked (black line) to four cleaved half sites (red and green arrows). (B) A tetramer of resolvase (left) recombines two site I DNAs [same as in (A)]. Two models of resolvase strand exchange (right) are domain swap (top) and subunit rotation (bottom). The interfaces formed by E helices (blue and red sticks) are intact in the domain swap model but rotate relative to each other in the subunit rotation model. (C) (Top) resolvase requires three sites to form the synaptic complex but performs recombination exclusively on site I. The length and spacing of these sites are shown. (Bottom) The sequence of the symmetrized site I analog used, with the bases of the original sequence of site I shown in italics above and below the mutated bases. The double-strand cleavage sites are shown in black arrows. Thymidines substituted by 5-bromo-2'-deoxyuridine in oligonucleotide derivatives are shown shaded in yellow. Nicks in the crystallographic substrates are opposite the dashes.

The above figure is reprinted by permission from the AAAs: Science (2005, 309, 1210-1215) copyright 2005.