Mitochondrial electron transport chain complexes I, III, and IV (ETC Complexes I, III, and IV)

The mitochondrial electron transport chain (ETC) complexes I, III, and IV are integral membrane protein assemblies located in the inner mitochondrial membrane that facilitate the transfer of electrons from electron donors to oxygen. Complex I (NADH:ubiquinone oxidoreductase) initiates the process by oxidizing NADH, while Complex III (ubiquinol-cytochrome c reductase) and Complex IV (cytochrome c oxidase) continue the electron transfer, coupled with the pumping of protons into the intermembrane space to create an electrochemical gradient for ATP production. These complexes are critical for cellular energy metabolism, and their dysfunction is a hallmark of various mitochondrial diseases and neurodegenerative disorders like Parkinson's disease. Pharmacologically, these complexes are targeted by a variety of agents; for instance, Metformin is known to mildly inhibit Complex I to exert its anti-diabetic effects, while potent inhibitors like cyanide or carbon monoxide target Complex IV, leading to rapid cellular asphyxiation. Understanding the modulation of these complexes is essential for developing therapies for metabolic syndromes, cancer, and age-related diseases.

Other names

Respiratory chain complexes I, III, and IVNADH:ubiquinone oxidoreductase (Complex I)Ubiquinol-cytochrome c reductase (Complex III)Cytochrome c oxidase (Complex IV)Oxidative phosphorylation system (OXPHOS)

Inhibition of electron transfer between redox centers, modulation of the mitochondrial membrane potential, and alteration of the rate of reactive oxygen species generation.