<p>Radical SAM domains catalyze diverse reactions, including unusual methylations, isomerization, sulphur insertion, ring formation, anaerobic oxidation and protein radical formation. Evidence exists that these proteins generate a radical species by reductive cleavage of S:-adenosylmethionine (SAM) through an unusual Fe-S centre [<cite idref="PUB00010539"/>, <cite idref="PUB00015124"/>].</p><p>This entry represents radical SAM domains that form an alpha/beta horseshoe structure [<cite idref="PUB00054243"/>].</p>