Flp Tyrosine-based site-specific recombinases (also called integrases), C-terminal catalytic domain.
Yeast Flp-like recombinases mediate the amplification of the 2 micron circular plasmid copy number by catalyzing the intra-molecular recombination between two inverted repeats during replication. They belong to the DNA breaking-rejoining enzyme superfamily, which also includes prokaryotic tyrosine recombinases and type IB topoisomerases. These enzymes share the same fold in their catalytic domain containing six conserved active site residues and the overall reaction mechanism. Flp-like recombinases are almost exclusively found in yeast and are highly diverged in sequence from the prokaryotic tyrosine recombinases. They cleave their target DNA in trans with a composite active site in which the catalytic tyrosine is provided by a promoter bound to a site other than the one being cleaved. Thus each active site within Flp complexes is assembled by domain swapping and contains catalytic residues from two different monomers. Two DNA segments are synapsed by the tetrameric enzyme, carrying the nucleophilic tyrosine in each active site with only two of the four monomers active at a given time. The catalytic domain is linked through a flexible loop to the N-terminal domain, which is largely responsible for non-specific DNA binding and isomerization. Its overall fold is similar to the SAM domain fold also found in the N-terminal domains of lambda integrase and XerD recombinase.
Comment:DNA Holliday junction is held in a square planar conformation by the tetramer
Comment:tetramer contains an active pair and an inactive pair of monomers; each active pair can make 2 shared active sites
Comment:forms a shared trans active site between the RHR triad of one monomer with the Tyr from a second monomer
Comment:Lys binds the scissile phosphate in the active pair; this orients Tyr in the isomerization step; Arg and His, the RHR triad, bind the scissile phosphate in both pairs of monomers
Jiyao W et al.(2023). "The conserved domain database in 2023.",