CRYSTAL-STRUCTURE OF THE SITE-SPECIFIC RECOMBINASE GAMMA-DELTA RESOLVASE COMPLEXED WITH A 34 BP CLEAVAGE SITE

The structure of gamma delta resolvase complexed with a 34 bp substrate DNA has been determined at 3.0 Angstrom resolution. The DNA is sharply bent by 60 degrees toward the major groove and away from the resolvase catalytic domains at the recombination crossover point. The C-terminal one third of resolvase, which was disordered in the absence of DNA, forms an arm and a 3-helix DNA-binding domain on the opposite side of the DNA from the N-terminal domain. The arms wrap around the minor groove of the central 16 bp, and the DNA-binding domains interact with the major grooves near the outer boundaries of the binding site. The resolvase dimer is asymmetric, particularly in the arm region, implying a conformational adaptability that may be important for resolvase binding to different DNA sites in the synaptosome. It also raises the possibility of a sequential single-strand cleavage mechanism.