The protein encoded by this gene belongs to the complex I 19 kDa subunit family. Mammalian complex I is composed of 45 different subunits. This protein has NADH dehydrogenase activity and oxidoreductase activity. It plays an important role in transfering electrons from NADH to the respiratory chain. The immediate electron acceptor for the enzyme is believed to be ubiquinone. Alternative splicing of this gene results in multiple transcript variants encoding different isoforms.