TRX-like [2Fe-2S] Ferredoxin (Fd) family, NAD-dependent formate dehydrogenase (FDH) beta subunit; composed of proteins similar to the beta subunit of NAD-linked FDH of Ralstonia eutropha, a soluble enzyme that catalyzes the irreversible oxidation of formate to carbon dioxide accompanied by the reduction of NAD to NADH. FDH is a heteromeric enzyme composed of four nonidentical subunits (alpha, beta, gamma and delta). The FDH beta subunit contains a NADH:ubiquinone oxidoreductase (Nuo) F domain C-terminal to a Fd-like domain without the active site cysteines. The absence of conserved metal-binding residues in the putative active site suggests that members of this subfamily have lost the ability to bind iron-sulfur clusters in the N-terminal Fd-like domain. The C-terminal NuoF domain is a component of Nuo, a multisubunit complex catalyzing the electron transfer of NADH to quinone coupled with the transfer of protons across the membrane. NuoF contains one [4Fe-4S] cluster and binds NADH and FMN.
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