How many molecules of mitochondrial complex I are in a cell?

Mitochondrial complex I is the only enzyme responsible for oxidation of matrix NADH and regeneration of NAD for catabolism. Nuclear and mtDNA mutations, assembly impairments, and enzyme damage are implicated in inherited diseases, ischemia-reperfusion injury, neurodegeneration, and tumorogenesis. Here we introduce a novel method to measure the absolute content of complex I.