Abstract
Cytochrome c oxidase (CcO) is the terminal enzyme of the energy-transducing mitochondrial electron transport chain. It is a hetero-oligomeric complex composed of both mitochondrially and nuclear-encoded subunits.
The biogenesis of CcO is sequential process that requires numerous specific accessory proteins, so-called assembly factors, which include translational activators, translocases, molecular chaperones, copper metallochaperones and heme a biosynthetic enzymes. In addition, the correct biogenesis of CcO requires an even greater number of proteins with broader substrate specificities.
Indeed, mitochondrial ATP-dependent proteases might play an important role in CcO biogenesis. Out of the four identified energy dependent mitochondrial proteases, three were shown to be involved in proteolysis of CcO subunits.
Besides their protein-quality control function these oligomeric complexes may function as molecular chaperones promoting productive folding and assembly of CcO subunits.