NADH:ubiquinone oxidoreductase (complex I) () is a respiratory-chain enzyme that catalyses the transfer of two electrons from NADH to ubiquinone in a reaction that is associated with proton translocation across the membrane (NADH + ubiquinone = NAD+ + ubiquinol) []. Complex I is a major source of reactive oxygen species (ROS) that are predominantly formed by electron transfer from FMNH(2). Complex I is found in bacteria, cyanobacteria (as a NADH-plastoquinone oxidoreductase), archaea [], mitochondria, and in the hydrogenosome, a mitochondria-derived organelle. In general, the bacterial complex consists of 14 different subunits, while the mitochondrial complex contains homologues to these subunits in addition to approximately 31 additional proteins [].This entry includes the NADH dehydrogenase [ubiquinone]1 alpha subcomplex subunit 12 (NDUFA12) and the NADH dehydrogenase [ubiquinone]1 alpha subcomplex assembly factor 2 (NDUFAF2). NDUFA12 is an accessory subunit of the mitochondrial membrane respiratory chain NADH dehydrogenase (Complex I) [, ]. NDUFA12 is believed not to be involved in catalysis []. NDUFAF2 is a paralogue of the structural subunit NDUFA12 and functions as an assembly factor [].
