Complex I is a large, multi-subunit enzyme complex that exhibits a sophisticated mechanism of catalysis. The enzyme operates through a series of redox reactions. Initially, NADH binds to Complex I and donates two electrons to the flavin mononucleotide (FMN) prosthetic group. These electrons are then transferred through a series of iron-sulfur (Fe-S) clusters to the quinone binding site, where ubiquinone is reduced to ubiquinol.
