Ligation activity of FLP recombinase. The strand ligation activity of a site-specific recombinase using an activated DNA substrate.

The FLP protein of the 2-microns plasmid of yeast belongs to the integrase family of site-specific recombinases whose members form a covalent bond between a conserved tyrosine of the recombinase and the 3'-phosphoryl group at the site of cleavage. We have made an activated DNA substrate and have shown that FLP can promote efficient strand ligation without forming a covalent intermediate with the DNA substrate. The strand ligation activity of FLP is independent of its ability to cleave DNA. Since site-specific recombinases are members of the larger class of topoisomerases, these findings may be generally applicable to other members of this class of enzymes.