Fig. 1.

Mitochondrial redox flux and signaling. A. Nutrient catabolism and the liberation of electrons is coupled to the formation of NADH and NADPH which are utilized to support pro-oxidant and antioxidant activities in mitochondria. This results in spatiotemporal changes in mitochondrial redox buffering networks conveying signals that regulate protein function through cysteine switches. B. 10 potential sites for H₂O₂ production by mitochondria (represented by red star). Note the topology of H₂O₂ formation relative to the mitochondrial inner membrane. Sites include Complex I, Complex II (succinate dehydrogenase; Sdh), Complex III, 2-oxoglutarate dehydrogenase (Odh), pyruvate dehydrogenase (Pdh), branched-chain keto acid dehydrogenase (Bckdh), electron-transferring flavoprotein-ubiquinone oxidoreductase (Etfqo), sn-glycerol-3-phosphate dehydrogenase (G3PDH), dihydroorotate dehydrogenase (Dhodh), and sulfide quinone oxidoreductase (Sqr). FMN-Complex I; I_F, quinone binding site Complex I; I_Q, FAD-Complex II; II_F, quinone binding site Complex II; II_Q, quinone binding site outer leaflet Complex III; III_Qo, quinone binding site inner leaflet Complex III; III_Qi, 2-oxoglutarate; 2-OG, branched chain amino acid; Bcaa, dihydroorotate; Dho. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)