Figure 1

The mitochondrial electron transport chain complexes are encoded by two genetic systems: the mitochondrial DNA (mtDNA) and the nuclear DNA (nDNA). The mtDNA codes for 7 NADH dehydrogenase (ND) subunits for complex I, a cytochrome b for complex III, 3 cytochrome c oxidase (COX) subunits for complex IV, and 2 ATPase (ATPase6/8) for complex V. Complex II is solely encoded by nDNA. The solid arrows indicate the direction of electron flow in the respiration chain; dashed arrows indicate the flow of genetic information from mtDNA or nDNA to RNA to protein; the numbers indicate the actual number of protein subunits coded by each genetic system. Specific inhibitors of RNA transcription or protein translation with relative selectivity for each genetic system are indicated in blue.