Part of a membrane-bound complex that couples electron transfer with translocation of ions across the membrane. Required to maintain the reduced state of SoxR. Binds 2 [4Fe-4S] clusters per subunit. The complex is composed of six subunits: RsxA, RsxB, RsxC, RsxD, RsxE and RsxG. Belongs to the 4Fe4S bacterial-type ferredoxin family. RnfC subfamily.