NADH Dehydrogenase 1 Beta Subcomplex 4(NDUFB4) is a member of the complex I NDUFB4 subunit family. NDUFB4 is a non-catalytic subunit of the multisubunit NADH:ubiquinone oxidoreductase, which is the first enzyme complex in the mitochondrial electron transport chain(complex I). Mammalian complex I is comprised of 45 different subunits and transfers electrons from NADH to ubiquinone.