A central functional role for the 49-kDa subunit within the catalytic core of mitochondrial complex I

J Biol Chem. 2001 Jun 29;276(26):24082-7. doi: 10.1074/jbc.M102296200. Epub 2001 May 7.


We have analyzed a series of eleven mutations in the 49-kDa protein of mitochondrial complex I (NADH:ubiquinone oxidoreductase) from Yarrowia lipolytica to identify functionally important domains in this central subunit. The mutations were selected based on sequence homology with the large subunit of [NiFe] hydrogenases. None of the mutations affected assembly of complex I, all decreased or abolished ubiquinone reductase activity. Several mutants exhibited decreased sensitivities toward ubiquinone-analogous inhibitors. Unexpectedly, seven mutations affected the properties of iron-sulfur cluster N2, a prosthetic group not located in the 49-kDa subunit. In three of these mutants cluster N2 was not detectable by electron-paramagnetic resonance spectroscopy. The fact that the small subunit of hydrogenase is homologous to the PSST subunit of complex I proposed to host cluster N2 offers a straightforward explanation for the observed, unforeseen effects on this iron-sulfur cluster. We propose that the fold around the hydrogen reactive site of [NiFe] hydrogenase is conserved in the 49-kDa subunit of complex I and has become part of the inhibitor and ubiquinone binding region. We discuss that the fourth ligand of iron-sulfur cluster N2 missing in the PSST subunit may be provided by the 49-kDa subunit.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Binding Sites
  • Conserved Sequence
  • Cysteine / genetics
  • Electron Transport Complex I
  • Fungal Proteins / chemistry
  • Fungal Proteins / genetics
  • Fungal Proteins / metabolism
  • Histidine / genetics
  • Hydrogenase / chemistry
  • Mitochondria / drug effects
  • Mitochondria / enzymology*
  • Models, Chemical
  • Molecular Sequence Data
  • Mutation
  • NADH, NADPH Oxidoreductases / chemistry*
  • NADH, NADPH Oxidoreductases / genetics
  • NADH, NADPH Oxidoreductases / metabolism
  • Protein Structure, Tertiary
  • Protein Subunits
  • Saccharomycetales / enzymology*
  • Sequence Homology, Amino Acid
  • Ubiquinone / metabolism


  • Fungal Proteins
  • Protein Subunits
  • Ubiquinone
  • Histidine
  • nickel-iron hydrogenase
  • Hydrogenase
  • NADH, NADPH Oxidoreductases
  • Electron Transport Complex I
  • Cysteine