This domain is found at the N-terminal of radical SAM proteins from bacteria and archaea. Proteins containing this domain are thought to catalyse diverse reactions, including methylations, isomerization, ring formation, anaerobic oxidation and protein radical formation [1, 2]. The function of this domain is unknown.

1: Radical SAM, a novel protein superfamily linking unresolved steps in familiar biosynthetic pathways with radical mechanisms: functional characterization using new analysis and information visualization methods. Sofia HJ, Chen G, Hetzler BG, Reyes-Spindola JF, Miller NE; Nucleic Acids Res 2001;29:1097-1106. PMID:11222759