{PDOC00521}
{PS00535; COMPLEX1_49K}
{BEGIN}
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* Respiratory-chain NADH dehydrogenase 49 Kd subunit signature *
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Respiratory-chain NADH dehydrogenase (EC 1.6.5.3) [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.

-Consensus pattern: [LIVMH]-H-[RT]-[GA]-x-E-K-[LIVMTN]-x-E-x-[KRQ]
-Sequences known to belong to this class detected by the pattern: ALL.
-Other sequence(s) detected in Swiss-Prot: NONE.
-Last update: December 2001 / Pattern and text revised.

[ 1] Ragan C.I.
     Curr. Top. Bioenerg. 15:1-36(1987).
[ 2] Weiss H., Friedrich T., Hofhaus G., Preis D.
     "The respiratory-chain NADH dehydrogenase (complex I) of
     mitochondria."
     Eur. J. Biochem. 197:563-576(1991).
     PubMed=2029890
[ 3] Fearnley I.M., Walker J.E.
     "Conservation of sequences of subunits of mitochondrial complex I and
     their relationships with other proteins."
     Biochim. Biophys. Acta 1140:105-134(1992).
     PubMed=1445936
[ 4] Weidner U., Geier S., Ptock A., Friedrich T., Leif H., Weiss H.
     "The 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."
     J. Mol. Biol. 233:109-122(1993).
     PubMed=7690854

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