Figure 10.

Proposed model for alteration of mitochondrial electron transport in the ppr40-1 mutant compared to wild type. In wild-type mitochondria, electrons flow through either Complexes I-III-IV or Complexes II-III-IV consuming oxygen and producing water. NADH is an electron donor for Complex I, whereas succinate provides electrons for Complex II. In the ppr40-1 mutant, the electron flow is reduced by dysfunction of Complex III enhancing the use alternative substrates of Complex IV, such as ascorbate. Reduced Complex III generates excess electrons producing superoxide, which is converted to hydrogen peroxide by MnSOD. AOX can contribute to the electron flow reducing the electron excess and superoxide pool.