Has menaquinol-oxidizing activity. HmeB subunit may function as a menaquinol-oxidizing site. HmeA, HmeB and HmeE subunits may together catalyze electron transfer from menaquinol to cytochrome c. Consists of five subunits: an integral membrane subunit, a cytochrome b-like subunit, a cytochrome c subunit and two iron-sulfur subunits. Belongs to the NrfD family.