KDR::GS is an artificial derivative of the recombinase encoded by the Kluyveromyces lactis pKD1 plasmid (UniProtKB:P13783), in which the 'GeneSwitch' sequence (a truncated ligand-binding domain from the Homo sapiens progesterone receptor) has been fused to the recombinase. This results in a protein with weak activity compared to the wild-type sequence, while the target specificity is unchanged. KDR::GS recognizes the KDRT target site, with recombination occurring between a pair of these sites (FBrf0228639).