FLPD5 represents a variant of the FLP recombinase encoded by the Saccharomyces cerevisiae 2μ plasmid in which codon 5 is an Asp residue. This variant affects the activity of the recombinase rather than its target-site specificity: FLPD5 has more than 10-fold greater activity than FLPG5 (FBrf0214794). FLPD5 mediates recombination between a pair of specific target sites, with compatible target sites corresponding to the wild-type FRT site and some of its derivatives. The minimal FRT target site is composed of two 13bp inverted repeats flanking an 8bp asymmetric spacer sequence (PMID:3879971). Recombination occurs between a pair of target sites oriented in the same direction; the 13bp repeats each act as binding sites for the recombinase (PMID:3047402), while the asymmetric 8bp spacer is the site of DNA strand exchange and determines the orientation of the target site (PMID:3711092). In addition to being compatible with the wild-type FRT site, FLPD5 is expected to be compatible with any engineered FRT variant that contains a mutation only in the spacer region. However, FLPD5 may be incompatible or show reduced recombination efficiency with FRT derivatives that contain mutations in their inverted repeats, since these mutations can affect the ability of the recombinase to bind the target site. The recombination event catalyzed by FLPD5 results in genetic modification, the nature of which is influenced by the relative orientation (direct or inverted), location and composition of the two target sites. The types of possible modification include deletion of DNA, generation of chromosomal rearrangements, integration of DNA into the genome, and replacement of genetic material with that from a donor plasmid using recombinase-mediated cassette exchange (RMCE) (reviewed in FBrf0231034).
