Affiliations: Dipartimento di Biochimica "G. Moruzzi",
Università di Bologna, Bologna, Italy
Note: [] Address for correspondence: Dr. Maria Luisa Genova, Dipartimento
di Biochimica "G. Moruzzi", Via Irnerio 48, 40126 Bologna, Italy. Tel.: +39 051
2091204; Fax: +39 051 2091224; E-mail: marialuisa.genova@unibo.it
Abstract: In this review we examine early and recent evidence for an
aggregated organization of the mitochondrial respiratory chain. Blue Native
Electrophoresis suggests that in several types of mitochondria Complexes I, III
and IV are aggregated as fixed supramolecular units having stoichiometric
proportions of each individual complex. Kinetic evidence by flux control
analysis agrees with this view, however the presence of Complex IV in bovine
mitochondria cannot be demonstrated, presumably due to high levels of free
Complex. Since most Coenzyme Q appears to be largely free in the lipid bilayer
of the inner membrane, binding of Coenzyme Q molecules to the Complex
I–III aggregate is forced by its dissociation equilibrium; furthermore
free Coenzyme Q is required for succinate-supported respiration and reverse
electron transfer. The advantage of the supercomplex organization is in a more
efficient electron transfer by channelling of the redox intermediates and in
the requirement of a supramolecular structure for the correct assembly of the
individual complexes. Preliminary evidence suggests that dilution of the
membrane proteins with extra phospholipids and lipid peroxidation may disrupt
the supercomplex organization. This finding has pathophysiological
implications, in view of the role of oxidative stress in the pathogenesis of
many diseases.
Keywords: Coenzyme Q, bound, pool, respiratory chain, supercomplexes, flux control analysis, electron channelling
Journal: BioFactors, vol. 25, no. 1-4, pp. 5-20, 2005
