Mitochondrial Bioenergetics Pathways in Chlamydomonas

Abstract

Mitochondrion is the site where the Krebs cycle and oxidative phosphorylation (OXPHOS) take place. After a brief overview of Krebs cycle and acetate metabolism in Chlamydomonas, this chapter focuses on OXPHOS components. OXPHOS is composed of five major multiprotein complexes: NADH:ubiquinone oxidoreductase (complex I), succinate dehydrogenase (complex II), ubiquinone: cytochrome c oxidoreductase (complex III), cytochrome c oxidase (complex IV), and ATP synthase. Three complexes (complexes I, III, and IV) pump protons from the matrix to the intermembrane space (IMS) and build a gradient which is used by ATP synthase to produce ATP. In Chlamydomonas and other eukaryotes, proteins forming these complexes have a dual genetic origin. A few proteins, mostly hydrophobic polypeptides, are mitochondrion-encoded, while the vast majority are nucleus-encoded and imported from the cytoplasm. Here we will review our current knowledge about these complexes.