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. 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 HdrB family.