<p>This entry represents the C-terminal subdomain of 5' to 3' exonucleases. The 5'-3' exonucleases are conserved in organisms as diverse as bacteriophage and mammals. The structure of this subdomain consists of 4-5 helices, which are packed into a bundle of two orthogonally packed alpha-hairpins. This domain is involved in interactions with DNA and proteins. 5' to 3' exonucleases that contain this domain include:</p><p> <ul> <li>Bacteriophage T4 RNase H, which has sequence similarity to the RAD2 family of eukaryotic proteins [<cite idref="PUB00011713"/>].</li><li>5' to 3' exonuclease domain of DNA polymerase Taq, which is homologous to Escherichia coli DNA polymerase I (pol I) [<cite idref="PUB00022733"/>, <cite idref="PUB00011715"/>].</li><li>Bacteriophage T5 5'-exonuclease, which are structure-specific endonucleases [<cite idref="PUB00011714"/>].</li><li>Flap endonuclease-1 (Fen-1 nuclease), a structure specific nuclease that is an essential enzyme for eukaryotic DNA replication and repair [<cite idref="PUB00011712"/>].</li> </ul> </p>