<p>The ferredoxin protein family are electron carrier proteins with an iron-sulphur cofactor that act in a wide variety of metabolic reactions. Ferredoxins can be divided into several subgroups depending upon the physiological nature of the iron-sulphur cluster(s) and according to sequence similarities. </p><p>This entry represents members of the 2Fe-2S ferredoxin family that have a general core structure consisting of beta(2)-alpha-beta(2), which includes putidaredoxin and terpredoxin, and adrenodoxin [<cite idref="PUB00016347"/>, <cite idref="PUB00016348"/>, <cite idref="PUB00016349"/>, <cite idref="PUB00016350"/>]. They are proteins of around one hundred amino acids with four conserved cysteine residues to which the 2Fe-2S cluster is ligated. This conserved region is also found as a domain in various metabolic enzymes and in multidomain proteins, such as aldehyde oxidoreductase (N-terminal), xanthine oxidase (N-terminal), phthalate dioxygenase reductase (C-terminal), succinate dehydrogenase iron-sulphur protein (N-terminal), and methane monooxygenase reductase (N-terminal).</p>