NADH:ubiquinone oxidoreductase ubiquinone-binding site (Complex I Q-site)

The Mitochondrial complex I Q-site is a critical hydrophobic pocket within NADH:ubiquinone oxidoreductase, the largest enzyme of the mitochondrial electron transport chain. It is located at the interface of several core subunits, including NDUFS2, NDUFS7, and the membrane-bound ND1, where it facilitates the reduction of ubiquinone (Coenzyme Q10) to ubiquinol (Fiedorczuk et al., 2016, Nature). This redox reaction is energy-coupled to the translocation of four protons across the inner mitochondrial membrane, contributing significantly to the electrochemical gradient used for ATP synthesis. Dysfunction of this site is a primary cause of mitochondrial encephalomyopathies and is heavily implicated in the pathogenesis of Parkinson's disease due to its role as a major source of superoxide radical production (Koopman et al., 2012, EMBO Mol Med). Pharmacologically, the Q-site is the target of various compounds, ranging from potent toxins like rotenone to therapeutic agents like metformin, which is thought to exert its metabolic benefits through mild, reversible inhibition of this site (Vial et al., 2019, Front Endocrinol). Understanding the structural biology of the Q-site is essential for developing targeted therapies for metabolic disorders and mitigating the effects of mitochondrial oxidative stress.

Other names

Ubiquinone-binding pocketCoenzyme Q binding siteComplex I Q-binding cavityNADH dehydrogenase ubiquinone-binding site

Inhibitors bind to the Q-site to block the transfer of electrons from the terminal iron-sulfur cluster (N2) to ubiquinone, preventing its reduction to ubiquinol and disrupting the proton-motive force required for ATP production (Hirst, 2013, Annu Rev Biochem).