An iron-sulfur protein. A single glycine residue in EC
2.3.1.54, formate C-acetyltransferase, is oxidized to the corresponding radical by transfer of H from its CH2 to AdoMet with concomitant cleavage of the latter. The reaction requires Fe2+. The first stage is reduction of the AdoMet to give methionine and the 5'-deoxyadenosin-5'-yl radical, which then abstracts a hydrogen radical from the glycine residue.