This family of proteins are accessory subunits of the mitochondrial membrane respiratory chain NADH dehydrogenase (Complex I). This subunit is not believed to be catalytic [1-2].

1: Sequences of 20 subunits of NADH:ubiquinone oxidoreductase from bovine heart mitochondria. Application of a novel strategy for sequencing proteins using the polymerase chain reaction. Walker JE, Arizmendi JM, Dupuis A, Fearnley IM, Finel M, Medd SM, Pilkington SJ, Runswick MJ, Skehel JM; J Mol Biol 1992;226:1051-1072. PMID:1518044

2: cDNA of eight nuclear encoded subunits of NADH:ubiquinone oxidoreductase: human complex I cDNA characterization completed. Loeffen JL, Triepels RH, van den Heuvel LP, Schuelke M, Buskens CA, Smeets RJ, Trijbels JM, Smeitink JA; Biochem Biophys Res Commun 1998;253:415-422. PMID:9878551