Na⁺-translocating ferredoxin:NAD⁺ reductase (RnfABCDEG) complex. The 6 subunits have 191, 274, 435, 310, 201 and 189 aas, respectively (Vitt et al. 2022). Microbial metabolism often uses H⁺/Na⁺-translocating ferredoxin:NAD⁺ reductase (Rnf), either to exergonically oxidize reduced ferredoxin by NAD⁺ for generating a transmembrane electrochemical potential, or reversely to exploit the latter for producing reduced ferredoxin. The electron transfer route between ferredoxin and NAD via eight [4Fe-4S] clusters, one Fe ion and four flavins crossing the cell membrane twice related to the pathway of NADH:ubiquinone reductase. Redox-coupled Na⁺ translocation is provided by orchestrating Na⁺ uptake/release, electrostatic effects of the assumed membrane-integrated FMN semiquinone anion and accompanied polypeptide rearrangements mediated by different redox steps (Vitt et al. 2022).