Recent studies on site-specific DNA recombination reactions have provi
ded new information on the structure of the DNA-binding and catalytic
domains of the related Hin and gamma delta resolvase recombinases, res
pectively, and the interaction of the recombinational enhancer protein
Fis with DNA. These advances lay the foundation for detailed structur
al studies of recombination complexes and for elucidating the enzymolo
gy of DNA strand exchange in this family of recombinases.