<p>This domain is found in a diverse range of phosphoesterases [<cite idref="PUB00019430"/>], including protein phosphoserine phosphatases, nucleotidases, sphingomyelin phosphodiesterases and 2'-3' cAMP phosphodiesterases, as well as nucleases such as bacterial SbcD or yeast MRE11. The most conserved regions in this domain centre around the metal chelating residues.</p>