A pathogenic cytochrome b mutation reveals new interactions between subunits of the mitochondrial bc1 complex.
Energy transduction in mitochondria involves five oligomeric complexes embedded within the inner membrane. They are composed of catalytic and noncatalytic subunits, the role of these latter proteins often being difficult to assign. One of these complexes, the bc1 complex, is composed of three catalytic subunits including cytochrome b and seven or eight noncatalytic subunits. Recently, several mutations in the human cytochrome b gene have been linked to various diseases. We have studied in detail the effects of a cardiomyopathy generating mutation G252D in yeast. This mutation disturbs the biogenesis of the bc1 complex at 36 degrees C and decreases the steady-state level of the noncatalytic subunit Qcr9p. In addition, the G252D mutation and the deletion of QCR9 show synergetic defects that can be partially bypassed by suppressor mutations at position 252 and by a new cytochrome b mutation, P174T. Altogether, our results suggest that the supernumerary subunit Qcr9p enhances or stabilizes the interactions between the catalytic subunits, this role being essential at high temperature.
Saint-Georges
Yann
Y
Centre de Génétique Moléculaire du CNRS, Avenue de la Terrasse, 91198-Gif sur Yvette, France.
Bonnefoy
Nathalie
N
di Rago
Jean Paul
JP
Chiron
Stephane
S
Dujardin
Geneviève
G
D000595:Amino Acid Sequence; D000818:Animals; D009202:Cardiomyopathies / Q000235:genetics*; D020134:Catalytic Domain; D003062:Codon; D003573:Cytochrome b Group / Q000235:genetics*; D004579:Electron Transport; D014450:Electron Transport Complex III / Q000235:genetics* / Q000378:metabolism*; D004583:Electrons; D005838:Genotype; D005998:Glycine / Q000737:chemistry; D006801:Humans; D015151:Immunoblotting; D007438:Introns; D008928:Mitochondria / Q000378:metabolism*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009154:Mutation; D010743:Phospholipids / Q000378:metabolism; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D012441:Saccharomyces cerevisiae / Q000201:enzymology; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics* / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D013696:Temperature; D013997:Time Factors
D003062:Codon; D003573:Cytochrome b Group; D010743:Phospholipids; C470793:QCR9 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D014450:Electron Transport Complex III; D005998:Glycine