InterPro domain: IPR008995

Transport of molybdenum into bacteria involves a high-affinity ABC transporter system whose expression is controlled by a repressor protein called ModE. While molybdate transport is tightly coupled to utilization in some bacteria, other organisms have molybdenum storage proteins. One class of putative molybdate storage proteins is characterised by a sequence consisting of about 70 amino acids (Mop). A tandem repeat of Mop sequences also constitutes the molybdate binding domain of ModE.

The 7kDa Mop protein from the methanol-utilizing anaerobe Sporomusa ovata occurs as highly symmetric hexamers binding eight oxyanions. Each peptide assumes an OB fold, which has previously also been observed in ModE. Each hexameric Mop molecule contains eight metal binding sites of two different types; all of them are only formed upon oligomer assembly, i.e., each binding site is located on the interface between two or three dimers [ 1 ].

1. Structure of the molybdate/tungstate binding protein mop from Sporomusa ovata. Structure 8, 1127-36