Asymmetry in active complexes of FLP recombinase

The FLP recombinase promotes a site-specific recombination reaction in the 2mu plasmid of yeast. The protein-DNA complex that carries out the reaction is asymmetric. Three FLP monomers bound to specific FLP-recognition sequences are required to efficiently carry out one set of reciprocal DNA cleavage and strand exchange events on a Holliday junction substrate. If a fourth monomer plays an auxiliary role in the reaction, it is bound without sequence specificity. The data suggest a modified model for cleavage of DNA in trans by the FLP recombinase that might help reconcile some seemingly conflicting resulted obtained with integrase class recombinases.