Flap endonucleases (FENs, also known as 5' durgs in older references) are a class of nucleolytic enzymes that act as both 5'-3' exonucleases and structure-specific

endonucleases Endonucleases are enzymes that cleave the phosphodiester bond within a polynucleotide chain. Some, such as deoxyribonuclease I, cut DNA relatively nonspecifically (without regard to sequence), while many, typically called restriction endonucleases ...

on specialised DNA structures that occur during the biological processes of

DNA replication In molecular biology, DNA replication is the biological process of producing two identical replicas of DNA from one original DNA molecule. DNA replication occurs in all living organisms acting as the most essential part for biological inheritanc ...

DNA repair DNA repair is a collection of processes by which a cell identifies and corrects damage to the DNA molecules that encode its genome. In human cells, both normal metabolic activities and environmental factors such as radiation can cause DNA da ...

, and DNA recombination. Flap endonucleases have been identified in eukaryotes, prokaryotes, archaea, and some

virus A virus is a submicroscopic infectious agent that replicates only inside the living cells of an organism. Viruses infect all life forms, from animals and plants to microorganisms, including bacteria and archaea. Since Dmitri Ivanovsk ...

es. Organisms can have more than one FEN homologue; this redundancy may give an indication of the importance of these enzymes. In prokaryotes, the FEN enzyme is found as an N-terminal domain of

DNA polymerase A DNA polymerase is a member of a family of enzymes that catalyze the synthesis of DNA molecules from nucleoside triphosphates, the molecular precursors of DNA. These enzymes are essential for DNA replication and usually work in groups to create ...

I, but some prokaryotes appear to encode a second homologue. The endonuclease activity of FENs was initially identified as acting on a DNA duplex which has a single-stranded 5' overhang on one of the strands (termed a "5' flap", hence the name flap endonuclease). FENs catalyse hydrolytic cleavage of the

phosphodiester bond In chemistry, a phosphodiester bond occurs when exactly two of the hydroxyl groups () in phosphoric acid react with hydroxyl groups on other molecules to form two ester bonds. The "bond" involves this linkage . Discussion of phosphodiesters is d ...

at the junction of single- and double-stranded DNA. Some FENs can also act as 5'-3' exonucleases on the 5' terminus of the flap strand and on 'nicked' DNA substrates.

Protein structure Protein structure is the three-dimensional arrangement of atoms in an amino acid-chain molecule. Proteins are polymers specifically polypeptides formed from sequences of amino acids, the monomers of the polymer. A single amino acid monom ...

models based on

X-ray crystallography X-ray crystallography is the experimental science determining the atomic and molecular structure of a crystal, in which the crystalline structure causes a beam of incident X-rays to diffract into many specific directions. By measuring the angles ...

data suggest that FENs have a flexible arch created by two α-helices through which the single 5' strand of the 5' flap structure can thread. Flap endonucleases have been used in

biotechnology Biotechnology is the integration of natural sciences and engineering sciences in order to achieve the application of organisms, cells, parts thereof and molecular analogues for products and services. The term ''biotechnology'' was first used ...

, for example the Taqman PCR assay and the Invader Assay for mutation and single nucleotide polymorphism (SNP) detection.

References

External links

External lin
Flap endonucleases, 5'-3' exonucleases & 5' nucleases
{{DNA replication Biotechnology EC 3.1

See also

References

External links