Part of a membrane-bound complex that couples electron transfer with translocation of ions across the membrane. Couples electron transfer from reduced ferredoxin to NAD(+) with translocation of H(+) out of the cell. Essential for energy conservation during autotrophic growth. Contributes to ATP synthesis during heterotrophic growth. The complex is composed of six subunits: RnfA, RnfB, RnfC, RnfD, RnfE and RnfG. Belongs to the NqrDE/RnfAE family.