Protein Domain : Radical SAM IPR007197

Type	Domain
Description	Radical SAM proteins are found in all domains of life and share an unusual Fe-S cluster associated with generation of a free radical by reductive cleavage of SAM and often provide an anaerobic or oxygen-independent mechanism that is found as an aerobic reaction in other proteins. Radical SAM proteins catalyse diverse reactions, including unusual methylations, isomerization, sulphur insertion, ring formation, anaerobic oxidation and protein radical formation. These proteins function in DNA precursor, vitamin, cofactor, antibiotic and herbicide biosynthesis and in biodegradation pathways [ , ].Radical SAM proteins share several common features, notably three strictly conserved cysteine residues generally included in the CxxxCxxC motif. These critical cysteines coordinate the unusual [4Fe-4S]2+/1+ cluster, while SAM serves as ligand for the fourth iron atom and acts as a cofactor or a cosubstrate []. The radical SAM enzymes biochemically characterised to date have in common the cleavage of the [4Fe-4S]1+-SAM complex to [4Fe-4S]2+-Met and the 5'-deoxyadenosyl radical, which abstracts a hydrogen atom from the substrate to initiate a radical mechanism [, ].The Radical SAM domain is organised in a fold related to the β-barrel or TIM barrel, in which β-strands are arranged in a barrel-like array, with peripheral helices intervening between β-strands. The [4Fe-4S] clusters and substrates are bound within the barrels, as is typical of TIM barrel enzymes [, ].
Short Name	rSAM