NADH:ubiquinone oxidoreductase, B18 subunit (IPR008698)

Short name: NADH_UbQ_OxRdtase_B18_su

Overlapping homologous superfamilies


Family relationships



NADH:ubiquinone oxidoreductase (complex I) (EC: 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) [PMID: 1470679]. 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 [PMID: 10940377], 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 [PMID: 18394423].

This family consists of several NADH-ubiquinone oxidoreductase B18 subunit proteins from different eukaryotic organisms. Oxidative phosphorylation is the well-characterised process in which ATP, the principal carrier of chemical energy of individual cells, is produced due to a mitochondrial proton gradient formed by the transfer of electrons from NADH and FADH2 to molecular oxygen. The oxidative phosphorylation (OXPHOS) system is located in the mitochondrial inner membrane and consists of five multi-subunit enzyme complexes and two small electron carriers: coenzyme Q10 and cytochrome C. At least 70 structural proteins involved in the formation of the whole OXPHOS system are encoded by nuclear genes, whereas 13 structural proteins are encoded by the mitochondrial genome. Deficiency of NADH ubiquinone oxidoreductase, the first enzyme complex of the mitochondrial respiratory chain, is one of the most frequent causes of Homo sapiens mitochondrial encephalomyopathies [PMID: 10830904].

GO terms

Biological Process

No terms assigned in this category.

Molecular Function

GO:0008137 NADH dehydrogenase (ubiquinone) activity
GO:0003954 NADH dehydrogenase activity

Cellular Component

GO:0005739 mitochondrion

Contributing signatures

Signatures from InterPro member databases are used to construct an entry.