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. Was originally (PubMed:8969503, PubMed:9384377) predicted to be the product of two different genes yfkA and yfkB. Truncated N-terminus.