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NADH:ferredoxin oxidoreductase

RnfABCDEG of Rhodobacter capsulatus

The Rnf-type NADH dehydrogenase, RnfABCDEG (Imkamp et al., 2007). Note: RnfD may be truncated as almost all homologues have 300-330aas with 6-7 TMSs.  This system has been shown to pump Na+ out of the cell when reducing NAD+ with reduced ferredoxin, and dependent on the smf for reduction of ferredoxin with NADH2 (Hess et al. 2013).

RnfABCDEG of Acetobacterium woodii:
RnfA (195 aas) (C4N8U4)
RnfB (333 aas) (C4N8U5)
RnfC (443aas) (C4N8U0)
RnfD (132aas) (C4N8U1)
RnfE (196 aas) (C4N8U3)
RnfG (207 aas) (C4N8U2)

The Rnf-type NADH dehydrogenase, RnfABCDEG/MA0658 (Welte and Deppenmeier 2013). RnfB and RnfC are on the cytoplasmic side of the membrane. Both have 4Fe4S centers (5 and 2, repectively), and RnfB oxidizes reduced ferredoxin (Suharti et al. 2014). The integral membrane proteins are RnfA, D and E, while RnfG and MA0658 are on the outside. RnfE reduces oxidized Mph (Welte and Deppenmeier 2013).

RnfABCDEG/MA0658 complex of Methanosarcina acetivorans
RnfA, 199 aas
RnfB, 264 aas
RnfC, 447 aas
RnfD, 288 aas
RnfE, 213 aas
RnfG, 188 aas
MA0658, 500 aas

Rnf-type NADH dehydrogenase, RsxA, RsxD, RsxE, RsxG, RsxB, RsxC of 6, 10, 5, 1, 1 and 1 TMSs, respectively.

Rnf-like system, RsxA, B, C, D, E, G of E. coli

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).


Terrabacteria group
RnfABCDEG of Clostridium tetanomorphum