Flippase (Flp)
Site-specific recombinase from yeast that catalyzes recombination between FRT sites. Native enzyme shows thermostability issues in mammalian cells, addressed through engineered variants FLPe and FLPo with improved recombination efficiency at 37°C.
Origin: Saccharomyces cerevisiae
Characteristics
Member of λ integrase family that recognizes 34 bp FRT (Flippase Recognition Target) sites. Native FLP exhibits thermostability issues at mammalian temperatures (37°C) resulting in poor recombination efficiency. FLPe variant shows 4-fold improvement but achieves only ~6% efficiency with mosaic recombination. Codon-optimized FLPo variant achieves recombination efficiency similar to Cre through mouse codon usage, removal of cryptic splice sites, and enhanced mRNA stability.
Applications: Conditional gene activation and inactivation in mammalian cells and model organisms. Enables FRT-mediated cassette exchange for genetic manipulation. Used in combination with Cre-loxP system for complex multi-recombinase genetic strategies. Facilitates marker excision and chromosomal rearrangements in transgenic animals and cultured cells.
Limitations: Native FLP recombinase shows poor thermostability at mammalian temperatures, limiting efficiency in cultured cells and animals. FLPe variant achieves only ~6% recombination efficiency compared to Cre. Requires codon-optimized FLPo variant for high-efficiency applications in mammalian systems. Less widely adopted than Cre-loxP system, resulting in fewer available transgenic tools and reporter lines.