Mitochondrial complex II ubiquinone binding site (CII Q-site)

Mitochondrial complex II, also known as succinate dehydrogenase (SDH) or succinate-ubiquinone oxidoreductase (SQR), is a multi-subunit enzyme complex that plays a dual role in the citric acid cycle and the mitochondrial electron transport chain (NIH, Wikipedia). It catalyzes the oxidation of succinate to fumarate and the reduction of ubiquinone to ubiquinol, facilitating the flow of electrons into the respiratory chain (NIH, ResearchGate). The ubiquinone binding sites (Q-sites), primarily located at the interface of the SDHB, SDHC, and SDHD subunits, are critical for this electron transfer process (NIH, PNAS). These sites are the primary targets for a diverse range of inhibitors, including agricultural fungicides such as carboxin and boscalid, as well as experimental anti-cancer compounds like alpha-tocopheryl succinate (NIH, MedChemExpress). In a clinical context, the Q-site is a significant therapeutic target because its inhibition can lead to the targeted generation of reactive oxygen species (ROS) and the induction of apoptosis in malignant cells (ResearchGate, Frontiers in Oncology). Mutations in the subunits forming these binding sites are frequently associated with hereditary cancer syndromes, such as paraganglioma and pheochromocytoma, where the resulting loss of enzyme activity leads to the accumulation of the oncometabolite succinate (NIH, PNAS). Furthermore, the Q-site is explored for its role in ischemia-reperfusion injury and as a target for anti-parasitic agents (PNAS, NIH). Understanding the structural and functional nuances of these binding sites is essential for developing selective drugs that can modulate mitochondrial metabolism and cellular signaling in various disease states (NIH, SCBT).

Other names

Succinate dehydrogenase ubiquinone binding siteSuccinate-ubiquinone reductase Q-siteSDH Q-siteComplex II Q-siteQuinone binding site of Complex IISuccinate-ubiquinone oxidoreductase ubiquinone binding site

Inhibition of electron transfer from succinate to ubiquinone by binding to the quinone-binding pocket (Q-site), which disrupts the mitochondrial respiratory chain and the citric acid cycle, often leading to the generation of reactive oxygen species (ROS) and induction of apoptosis (NIH, ResearchGate, Frontiers in Oncology).