Could serve in the delivery of heme to a membrane-localized target protein (Probable). Binds one molecule of heme per monomer, possibly covalently; heme and Fe-S cluster binding are independent. Incubation with the reductant sodium dithionite increases binding. Does not have coproporphyrinogen III dehydrogenase activity in vitro, does not complement an E.coli hemN deletion in vivo (PubMed:22142238). Binds 1 Fe-S cluster, it is probably [4Fe-4S]. The cluster is coordinated with 3 cysteines and an exchangeable S-adenosyl-L-methionine; only dimeric protein has the cluster (Probable). Homodimer. A minor, heme-containing fraction is associated with the cell membrane. L.lactis does not synthesize heme, but is able to take it up from growth medium and to incorporate it into cytochromes. Might carry two S-adenosyl-L-methionine binding sites with only one binding to the iron-sulfur cluster. Belongs to the anaerobic coproporphyrinogen-III oxidase family. HemW subfamily.