Involved in sulfur transfer in the conversion of molybdopterin precursor Z to molybdopterin. Cofactor biosynthesis; molybdopterin biosynthesis. Heterotetramer of 2 MoaD subunits and 2 MoaE subunits. Forms a stable heterotetrameric complex of 2 MoaD and 2 MoeB during adenylation of MoaD by MoeB. During catalysis MoaD shuttles between the two heterotetrameric complexes. By anaerobiosis, repressed by the molybdenum cofactor. C-terminal thiocarboxylation occurs in 2 steps, it is first acyl-adenylated (-COAMP) by MoeB, then thiocarboxylated (-COSH) by IscS. The measured mass is that of the thiolated protein. The measured mass is that of the thiolated protein. The cross-link is not seen in all structures of the MoaE-MoaD complex. Belongs to the MoaD family.