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

The Mitochondrial electron transport chain complex I Q-site is the specific binding pocket within NADH:ubiquinone oxidoreductase where ubiquinone (Coenzyme Q10) undergoes reduction to ubiquinol. This site is structurally formed by the interface of several subunits, including the mitochondrially encoded ND1 and the nuclear-encoded NDUFS2 and NDUFS7 subunits [Fiedorczuk et al., 2016, Nature]. Its primary biological function is to facilitate the transfer of electrons from the terminal iron-sulfur cluster (N2) to the quinone pool, a process coupled to the pumping of four protons across the inner mitochondrial membrane to drive ATP synthesis [Hirst, 2013, Annual Review of Biochemistry]. Dysregulation or genetic mutations at this site are central to the pathogenesis of mitochondrial diseases such as Leber Hereditary Optic Neuropathy (LHON) and Leigh syndrome [Chinnery, 2015, GeneReviews]. Furthermore, the Q-site is a significant source of reactive oxygen species (ROS) when electron flow is impeded, contributing to neurodegenerative conditions like Parkinson's disease [Vila et al., 2008, Trends in Molecular Medicine]. Many small molecules, including the pesticide rotenone and the anti-diabetic drug metformin, interact with this site to modulate mitochondrial respiration and cellular energy sensing [Bridges et al., 2014, PMID: 25043038].

Other names

Ubiquinone-binding pocket of Complex ICoenzyme Q binding siteNADH dehydrogenase (ubiquinone) Q-siteRotenone binding site

Inhibition of electron transfer from the terminal iron-sulfur cluster (N2) to ubiquinone, which prevents the reduction of Coenzyme Q and disrupts the proton gradient required for ATP synthesis [Hirst, 2013, Annual Review of Biochemistry].