NADH-ubiquinone oxidoreductase, 20 Kd subunit (IPR006138)

Short name: NADH_UQ_OxRdtase_20Kd_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].

Among the many polypeptide subunits that make up complex I, there is one with a molecular weight of 20 kDa (in mammals) [PMID: 1577158], which is a component of the iron-sulphur (IP) fragment of the enzyme. It seems to bind a 4Fe-4S iron-sulphur cluster. The 20 kDa subunit has been found to be nuclear encoded, as a precursor form with a transit peptide in mammals, and in Neurospora crassa. It is mitochondrial encoded in Paramecium (gene psbG) and chloroplast encoded in various higher plants (gene ndhK or psbG).

GO terms

Biological Process

GO:0055114 oxidation-reduction process

Molecular Function

GO:0051539 4 iron, 4 sulfur cluster binding
GO:0008137 NADH dehydrogenase (ubiquinone) activity
GO:0048038 quinone binding

Cellular Component

No terms assigned in this category.

Contributing signatures

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