Respiratory complex III is required to maintain complex I in mammalian mitochondria

Mol Cell. 2004 Mar 26;13(6):805-15. doi: 10.1016/s1097-2765(04)00124-8.


A puzzling observation in patients with oxidative phosphorylation (OXPHOS) deficiencies is the presence of combined enzyme complex defects associated with a genetic alteration in only one protein-coding gene. In particular, mutations in the mtDNA encoded cytochrome b gene are associated either with combined complex I+III deficiency or with only complex III deficiency. We have reproduced the combined complex I+III defect in mouse and human cultured cell models harboring cytochrome b mutations. In both, complex III assembly is impeded and causes a severe reduction in the amount of complex I, not observed when complex III activity was pharmacologically inhibited. Metabolic labeling in mouse cells revealed that complex I was assembled, although its stability was severely hampered. Conversely, complex III stability was not influenced by the absence of complex I. This structural dependence among complexes I and III was confirmed in a muscle biopsy of a patient harboring a nonsense cytochrome b mutation.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Cells, Cultured
  • Clone Cells
  • Codon, Nonsense
  • Cytochromes b / genetics
  • DNA, Mitochondrial / genetics
  • DNA, Mitochondrial / metabolism
  • Electron Transport Complex III / genetics
  • Electron Transport Complex III / metabolism*
  • Humans
  • L Cells
  • Mammals*
  • Mice
  • Mitochondria / enzymology
  • Mitochondria / genetics*
  • Models, Molecular
  • Mutagenesis, Site-Directed
  • Mutation, Missense
  • Oxidative Phosphorylation


  • Codon, Nonsense
  • DNA, Mitochondrial
  • Cytochromes b
  • Electron Transport Complex III