Evidence that the assembly of the yeast cytochrome bc1 complex involves the formation of a large core structure in the inner mitochondrial membrane

FEBS J. 2009 Apr;276(7):1900-14. doi: 10.1111/j.1742-4658.2009.06916.x. Epub 2009 Feb 19.


The assembly status of the cytochrome bc(1) complex has been analyzed in distinct yeast deletion strains in which genes for one or more of the bc(1) subunits were deleted. In all the yeast strains tested, a bc(1) sub-complex of approximately 500 kDa was found when the mitochondrial membranes were analyzed by blue native electrophoresis. The subsequent molecular characterization of this sub-complex, carried out in the second dimension by SDS/PAGE and immunodecoration, revealed the presence of the two catalytic subunits, cytochrome b and cytochrome c(1), associated with the noncatalytic subunits core protein 1, core protein 2, Qcr7p and Qcr8p. Together, these bc(1) subunits build up the core structure of the cytochrome bc(1) complex, which is then able to sequentially bind the remaining subunits, such as Qcr6p, Qcr9p, the Rieske iron-sulfur protein and Qcr10p. This bc(1) core structure may represent a true assembly intermediate during the maturation of the bc(1) complex; first, because of its wide distribution in distinct yeast deletion strains and, second, for its characteristics of stability, which resemble those of the intact homodimeric bc(1) complex. By contrast, the bc(1) core structure is unable to interact with the cytochrome c oxidase complex to form respiratory supercomplexes. The characterization of this novel core structure of the bc(1) complex provides a number of new elements clarifying the molecular events leading to the maturation of the yeast cytochrome bc(1) complex in the inner mitochondrial membrane.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Electron Transport Complex III / chemistry
  • Electron Transport Complex III / genetics
  • Electron Transport Complex III / metabolism*
  • Membrane Proteins / genetics
  • Membrane Transport Proteins / genetics
  • Membrane Transport Proteins / metabolism
  • Mitochondrial Membranes / metabolism*
  • Mitochondrial Proteins / genetics
  • Molecular Chaperones / genetics
  • Molecular Weight
  • Nuclear Proteins / genetics
  • Nuclear Proteins / metabolism
  • Protein Subunits / chemistry
  • Protein Subunits / genetics
  • Protein Subunits / metabolism
  • Saccharomyces cerevisiae / metabolism*
  • Saccharomyces cerevisiae Proteins / genetics
  • Saccharomyces cerevisiae Proteins / metabolism


  • BCS1 protein, S cerevisiae
  • Membrane Proteins
  • Membrane Transport Proteins
  • Mitochondrial Proteins
  • Molecular Chaperones
  • Nuclear Proteins
  • Protein Subunits
  • QCR10 protein, S cerevisiae
  • QCR6 protein, S cerevisiae
  • QCR9 protein, S cerevisiae
  • Rieske iron-sulfur protein
  • Saccharomyces cerevisiae Proteins
  • Electron Transport Complex III