| Primary Identifier | IPR038969 | Type | Family |
| Short Name | FEN |
| description | This entry represents a family of proteins that includes flap endonucleases from bacteria and viruses. Flap endonucleases (FENs) catalyse the exonucleolytic hydrolysis of blunt-ended duplex DNA substrates and the endonucleolytic cleavage of 5'-bifurcated nucleic acids at the junction formed between single and double-stranded DNA [].Escherichia phage T5 encodes the flap endonuclease D15, which catalyzes both the 5'-exonucleolytic and structure-specific endonucleolytic hydrolysis of DNA branched nucleic acid molecules [, , ]. In bacteriophage T4, disruption of the rnh gene (which encodes a FEN, known historically as T4 RNase H) results in slower, less accurate DNA replication. Bacteriophage T4 has both 5' nuclease and flap endonuclease activities []. In prokaryotes, the essential FEN reaction can be performed by the N-terminal 5'-3' exonuclease domain present on DNA polymerase I. Some eubacteria, however, possess a second FEN-encoding gene, in addition to their DNA polymerase I FEN domain [, ]. Two distinct classes of these independent bacterial FENs exist: ExoIX (Xni) from Escherichia coli and SaFEN (Staphylococcus aureus FEN). SaFEN has both FEN and 5'-3' exonuclease activities. Xni (also known as YgdG) was previously identified as a 3'-5' exonuclease and named exonuclease IX (exonuclease 9) [, ]but subsequently found to possess flap endonuclease activity, but not exonuclease activity [, , ]. |
