Mechanism
All redox reactions take place in the extramembranous portion of NADH dehydrogenase. NADH initially binds to NADH dehydrogenase, and transfers two electrons to the flavin mononucleotide (FMN) prosthetic group of complex I, creating FMNH2. The electron acceptor - the isoalloxazine ring - of FMN is identical to that of FAD. The electrons are then transferred through the second prosthetic group of NADH dehydrogenase via a series of iron-sulfur (Fe-S) clusters, and finally to coenzyme Q (ubiquinone). This electron flow changes the redox state of the protein, inducing conformational changes of the protein which alters the pK values of ionizable side chain, and causes four hydrogen ions to be pumped out of the mitochondrial matrix. Ubiquinone (CoQ) accepts two electrons to be reduced to ubiquinol (CoQH2).
Read more about this topic: NADH Dehydrogenase
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