Several structures of the 4Fe-4S ferredoxin domain have been determined [PMID: 7966291]. The clusters consist of two interleaved 4Fe- and 4S-tetrahedra forming a cubane-like structure, in such a way that the four iron occupy the eight corners of a distorted cube. Each 4Fe-4S is attached to the polypeptide chain by four covalent Fe-S bonds involving cysteine residues.
A number of proteins have been found [PMID: 2185975] that include one or more 4Fe-4S binding domains similar to those of bacterial-type ferredoxins.
The pattern of cysteine residues in the iron-sulphur region is sufficient to detect this class of 4Fe-4S binding proteins. This entry represents the whole domain.
Note:In some bacterial ferredoxins, one of the two duplicated domains has lost one or more of the four conserved cysteines. The consequence of such variations is that these domains have either lost their iron-sulphur binding property or bind to a 3Fe-3S centre instead of a 4Fe-4S centre.