The protein encoded by this gene is a subunit of the multisubunit NADH:ubiquinone oxidoreductase (complex I). Mammalian complex I is located at the mitochondrial inner membrane. This protein has NADH dehydrogenase activity and oxidoreductase activity. It transfers electrons from NADH to ubiquinone. Mutations in the human gene are associated with linear skin defects with multiple congenital anomalies 3 and mitochondrial complex I deficiency.