Mutations in the 2-microns circle site-specific recombinase that abolish recombination without affecting substrate recognition.

The site-specific recombinase encoded by the yeast plasmid 2-microns circle (FLP) forms a transient covalent linkage with its substrate DNA via a tyrosine residue, which appears to be located near its COOH terminus. The homology of the COOH terminus of FLP with that of the Int family of recombinases suggests that tyrosine-343 of FLP could be involved in forming the DNA-protein bridge. We have mutated tyrosine-343 to a phenylalanine or serine. We demonstrate that the binding of each of the two mutant proteins to its substrate is indistinguishable from that of wild-type FLP. However, both mutant proteins are incapable of catalyzing strand cleavage and recombination.