PROSITE documentation PDOC00521
Respiratory-chain NADH dehydrogenase 49 Kd subunit signature


Respiratory-chain NADH dehydrogenase (EC [1,2] (also known as complex I or NADH-ubiquinone oxidoreductase) is an oligomeric enzymatic complex located in the inner mitochondrial membrane which also seems to exist in the chloroplast and in cyanobacteria (as a NADH-plastoquinone oxidoreductase). Among the 25 to 30 polypeptide subunits of this bioenergetic enzyme complex there is one with a molecular weight of 49 Kd (in mammals), which is the third largest subunit of complex I and is a component of the iron-sulfur (IP) fragment of the enzyme. It seems to bind a 4Fe-4S iron-sulfur cluster. The 49 Kd subunit has been found to be:

  • Nuclear encoded, as a precursor form with a transit peptide in mammals, and in Neurospora crassa.
  • Mitochondrial encoded in protozoan such as Paramecium (ORF 400), Leishmania and Trypanosoma (MURF 3).
  • Chloroplast encoded in various higher plants (ORF 392).

The 49 Kd subunit is highly similar to [3,4]:

  • Subunit D of Escherichia coli NADH-ubiquinone oxidoreductase (gene nuoD).
  • Subunit NQO4 of Paracoccus denitrificans NADH-ubiquinone oxidoreductase.
  • Subunit 5 of Escherichia coli formate hydrogenlyase (gene hycE).
  • Subunit G of Escherichia coli hydrogenase-4 (gene hyfG).

As as signature pattern we selected a highly conserved region, located in the N-terminal section of this subunit.

Last update:

December 2001 / Pattern and text revised.


Technical section

PROSITE method (with tools and information) covered by this documentation:

COMPLEX1_49K, PS00535; Respiratory chain NADH dehydrogenase 49 Kd subunit signature  (PATTERN)


1AuthorsRagan C.I.
SourceCurr. Top. Bioenerg. 15:1-36(1987).

2AuthorsWeiss H. Friedrich T. Hofhaus G. Preis D.
TitleThe respiratory-chain NADH dehydrogenase (complex I) of mitochondria.
SourceEur. J. Biochem. 197:563-576(1991).
PubMed ID2029890

3AuthorsFearnley I.M. Walker J.E.
TitleConservation of sequences of subunits of mitochondrial complex I and their relationships with other proteins.
SourceBiochim. Biophys. Acta 1140:105-134(1992).
PubMed ID1445936

4AuthorsWeidner U. Geier S. Ptock A. Friedrich T. Leif H. Weiss H.
TitleThe gene locus of the proton-translocating NADH: ubiquinone oxidoreductase in Escherichia coli. Organization of the 14 genes and relationship between the derived proteins and subunits of mitochondrial complex I.
SourceJ. Mol. Biol. 233:109-122(1993).
PubMed ID7690854

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