<p>This entry represents the PP-loop motif superfamily [<cite idref="PUB00014303"/>,<cite idref="PUB00043328"/>]. The PP-loop motif appears to be a modified version of the P-loop of nucleotide binding domain that is involved in phosphate binding [<cite idref="PUB00014303"/>]. Named PP-motif, since it appears to be a part of a previously uncharacterised ATP pyrophophatase domain. ATP sulfurylases, <taxon tax_id="562">Escherichia coli</taxon> NtrL, and <taxon tax_id="1423">Bacillus subtilis</taxon> OutB consist of this domain alone. In other proteins, the pyrophosphatase domain is associated with amidotransferase domains (type I or type II), a putative citrulline-aspartate ligase domain or a nitrilase/amidase domain.</p>