InterPro: IPR017900 4Fe-4S ferredoxin, iron-sulphur binding, conserved site

This entry represents a conserved site of Fe-4S ferredoxin, iron-sulphur binding domain

Ferredoxins are iron-sulphur proteins that mediate electron transfer in a range of metabolic reactions; they fall into several subgroups according to the nature of their iron-sulphur cluster(s) [1, 2]. One group, originally found in bacteria, has been termed "bacterial-type", in which the active centre is a 4Fe-4S cluster. 4Fe-4S ferredoxins may in turn be subdivided into further groups, based on their sequence properties. Most contain at least one conserved domain, including four Cys residues that bind to a 4Fe-4S centre.

During the evolution of bacterial-type ferredoxins, intrasequence gene duplication, transposition and fusion events occured, resulting in the appearance of proteins with multiple iron-sulphur centres: e.g. dicluster-type (2[4Fe-4S]) and polyferredoxins, iron-sulphur subunits of bacterial succinate dehydrogenase/fumarate reductase, formate hydrogenlyase and formate dehydrogenase complexes, pyruvate-flavodoxin oxidoreductase, NADH:ubiquinone reductase, amongst others. In some bacterial ferredoxins, one of the duplicated domains has lost one or more of the four conserved Cys residues. These domains have either lost their iron-sulphur binding property, or bind to a 3Fe-4S centre instead of a 4Fe-4S centre. 3D structures are now known both for a number of monocluster-type [3] and dicluster-type [4] 4Fe-4S ferredoxins.