Part of a complex that catalyzes the reversible reduction of CoM-S-S-CoB to the thiol-coenzymes H-S-CoM (coenzyme M) and H-S-CoB (coenzyme B). coenzyme B + coenzyme M + methanophenazine = coenzyme M-coenzyme B heterodisulfide + dihydromethanophenazine Binds 2 [4Fe-4S] clusters per subunit. Cofactor metabolism; coenzyme M-coenzyme B heterodisulfide reduction; coenzyme B and coenzyme M from coenzyme M-coenzyme B heterodisulfide: step 1/1. The dihydromethanophenazine:CoB--CoM heterodisulfide reductase is composed of two subunits; HdrD and HdrE. Belongs to the HdrD family.