 These two 2Fe-2S cofactors each bind to the two distinct 150-kDa monomers of AO.Three separate domains harbor these three requirements.There is a 20 kDa N-terminal which binds to the two 2Fe-2S cofactors, a 40 kDa domain which provides a means of binding to the FAD, and a C-terminal which houses the molybdenum.