Editing Ferredoxin (section)

==== Membrane potential coupled reduction ====
Ferredoxin can also be reduced by using NADH (-320 mV) or {{chem|H|2}} (-414 mV), but these processes are coupled to the consumption of the [[membrane potential]] to power the "boosting" of electrons to the higher energy state.<ref name=Buckel2018/> The [[Rnf complex]] is a widespread membrane protein in [[bacteria]] that [[Reversible reaction|reversibly]] [[Electron transfer|transfers electrons]] between NADH and ferredoxin while pumping {{chem|Na|+}} or {{chem|H|+}} ions across the [[cell membrane]]. The [[chemiosmotic potential]] of the membrane is consumed to power the unfavorable reduction of {{chem|Fd|ox}} by NADH. This reaction is an essential source of {{chem|Fd|-|red}} in many [[autotroph]]ic organisms. If the [[Cell (biology)|cell]] is growing on [[Substrate (biology)|substrates]] that provide excess {{chem|Fd|-|red}}, the Rnf complex can transfer these electrons to {{chem|NAD|+}} and store the resultant energy in the membrane potential.<ref name="WestphalWiechmann2018">{{cite journal | vauthors = Westphal L, Wiechmann A, Baker J, Minton NP, Müller V | title = The Rnf Complex is an Energy-Coupled Transhydrogenase Essential to Reversibly Link Cellular NADH and Ferredoxin Pools in the Acetogen Acetobacterium woodii | journal = Journal of Bacteriology | volume = 200 | issue = 21 | date = November 2018 | pmid = 30126940 | doi = 10.1128/JB.00357-18 | pmc = 6182241 | doi-access = free }}</ref> The energy converting [[hydrogenase]]s (Ech) are a family of [[enzyme]]s that reversibly couple the transfer of electrons between {{chem|Fd}} and {{chem|H|2}} while pumping {{chem|H|+}} ions across the membrane to balance the energy difference.<ref name="SchoelmerichMüller2019">{{cite journal | vauthors = Schoelmerich MC, Müller V | title = Energy-converting hydrogenases: the link between H<sub>2</sub> metabolism and energy conservation | journal = Cellular and Molecular Life Sciences | volume = 77 | issue = 8 | pages = 1461–1481 | date = April 2020 | pmid = 31630229 | doi = 10.1007/s00018-019-03329-5 | s2cid = 204786346 | pmc = 11636919 }}</ref>

: {{chem|Fd|ox|''0''}} + {{chem|NADH}} + {{chem|Na|outside|+}} <chem><=></chem> {{chem|Fd|red|2-}} + {{chem| NAD|+}} + {{chem|Na|inside|+}}

: {{chem|Fd|ox|''0''}} + {{chem|H|2}} + {{chem|H|outside|+}} <chem><=></chem> {{chem|Fd|red|2-}} + {{chem| H|+}} + {{chem|H|inside|+}}