The Cytochrome c Oxidase subunit Cox26 participates in late steps of complex assembly

The Cytochrome c Oxidase subunit Cox26

participates in late steps of complex assembly

E-mail: mdjukan@gwdg.de

Mitochondria fulfill a wide array of functions within eukaryotic cells and are crucial for several metabolic pathways such as lipid biogenesis, amino acid and Fe/S cluster synthesis; they are also involved in cellular calcium storage and apoptosis. Known as the powerhouse of the cell, the mitochondrial oxidative phosphorylation system is the main source of ATP production. This process is driven by the respiratory chain, which is composed of a number of complexes acting in a sequential manner to transfer electrons from reduced substrates to oxygen through a series of oxidation-reduction reactions. Consisting of subunits of dual genetic origin, encoded either by the nuclear

or mitochondrial genome, the OXPHOS-system requires more than 30 assembly factors and helper proteins to arrange the structural subunits together with cofactors such as heme, Cu-Ions and FeS-clusters into functional complexes. This assembly

process is followed by further arrangement of the complexes into higher oligomeric structures, as shown for yeast complex III, IV and V. Cytochrome c oxidase is the terminal electron-transferring protein complex of the mitochondrial respiratory chain and consists of up to thirteen proteins and more than 20 assembly factors involved in its biogenesis. We have identified a novel Cytochrome c Oxidase subunit, Cox26, by isolation of respiratory chain supercomplexes from the yeast Saccharomyces cerevisiae followed by subsequent mass-spectrometric analysis. Cox26 is involved in the late steps of Cytochrome c Oxidase biogenesis and represents a structural

subunit of the enzyme. Absence of Cox26 in yeast affects respiratory growth on nonfermentable media and is linked to reduced Cytochrome c Oxidase enzyme activity.

Furthermore, Cox26 is required for proper assembly of the structural subunit Cox13.