Has oxidoreductase activity. The Hdl and Mvh subunits may together mediate electron transfer from hydrogen to an unidentified electron acceptor on the cytoplasmic side of the membrane. Binds 4 [4Fe-4S] clusters per subunit. The heterodisulfide reductase is composed of three subunits; HdlA, HdlB and HdlC. It forms a complex with the F420-non-reducing hydrogenase (Mvh), which provides the reducing equivalents to the heterodisulfide reductase. Belongs to the HdrA family.