<p> <taxon tax_id="1358">Lactococcus lactis</taxon> is one of the few organisms with two dihydroorotate dehydrogenases (DHODs) A and B [<cite idref="PUB00024613"/>]. The B enzyme is typical of DHODs in Gram-positive bacteria that use NAD+ as the second substrate. DHODB is a heterotetramer composed of a central homodimer of PyrDB subunits resembling the DHODA structure and two PyrK subunits along with three different cofactors: FMN, FAD, and a [2Fe-2S] cluster. The [2Fe-2S] iron-sulphur cluster binds to this C-terminal domain of the PyrK subunit, which is at the interface between the flavin and NAD binding domains and contains three beta-strands. The four cysteine residues at the N-terminal part of this domain are the ones that bind, in pairs, to the iron-sulphur cluster. The conformation of the whole molecule means that the iron-sulphur cluster is localized in a well-ordered part of this domain close to the FAD binding site [<cite idref="PUB00024613"/>]. The FAD and NAD binding domains are <db_xref db="INTERPRO" dbkey="IPR008333"/> and <db_xref db="INTERPRO" dbkey="IPR001433"/> respectively. </p> Dihydroorotate dehydrogenase, electron transfer subunit, iron-sulphur cluster binding domain