This family of bacterial proteins includes a sodium-translocating NADH-ubiquinone oxidoreductase (i.e. a respiration linked sodium pump). In Vibrio cholerae, it negatively regulates the expression of virulence factors through inhibiting (by an unknown mechanism) the transcription of the transcriptional activator ToxT [1]. The family also includes proteins involved in nitrogen fixation, RnfD and RnfE. The similarity of these proteins to NADH-ubiquinone oxidoreductases was previously noted [2].

1: Effects of changes in membrane sodium flux on virulence gene expression in Vibrio cholerae. Hase CC, Mekalanos JJ; Proc Natl Acad Sci U S A 1999;96:3183-3187. PMID:10077658

2: Membrane localization, topology, and mutual stabilization of the rnfABC gene products in Rhodobacter capsulatus and implications for a new family of energy-coupling NADH oxidoreductases. Kumagai H, Fujiwara T, Matsubara H, Saeki K; Biochemistry 1997;36:5509-5521. PMID:9154934