Conserved Site

NADH:ubiquinone oxidoreductase, 51kDa subunit, conserved site (IPR001949)

Short name: NADH-UbQ_OxRdtase_51kDa_CS


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 51kDa (in mammals), which is the second largest subunit of complex I and is a component of the iron-sulphur (IP) fragment of the enzyme. It seems to bind to NAD, FMN, and a 2Fe-2S cluster. The 51kDa subunit and the bacterial hydrogenase alpha subunit contain three regions of sequence similarities. The first one most probably corresponds to the NAD-binding site, the second to the FMN-binding site, and the third one, which contains three cysteines, to the iron-sulphur binding region.

GO terms

Biological Process

GO:0055114 oxidation-reduction process

Molecular Function

GO:0051539 4 iron, 4 sulfur cluster binding
GO:0010181 FMN binding
GO:0008137 NADH dehydrogenase (ubiquinone) activity

Cellular Component

No terms assigned in this category.

Contributing signatures

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