Binds 1 [4Fe-4S] cluster. The cluster is coordinated with 3 cysteines and an exchangeable S-adenosyl-L-methionine. Belongs to the radical SAM superfamily. The spacing between the conserved Cys residues used for the 4Fe-4S cluster is unusual (C-X11-CXXC instead of C-X3-CXXC); it is therefore unclear whether this protein will bind the cofactor.