Flavoprotein (FP) subunit of succinate dehydrogenase (SDH) that is involved in complex II of the mitochondrial electron transport chain and is responsible for transferring electrons from succinate to ubiquinone (coenzyme Q). Can act as a tumor suppressor. a quinone + succinate = a quinol + fumarate Carbohydrate metabolism; tricarboxylic acid cycle; fumarate from succinate (eukaryal route): step 1/1. Component of complex II composed of four subunits: the flavoprotein (FP) SDHA, iron-sulfur protein (IP) SDHB, and a cytochrome b560 composed of SDHC and SDHD (By similarity). Interacts with SDHAF2/SDH5; interaction is required for FAD attachment (By similarity). Interacts with TRAP1 (By similarity). Interacts with LACC1 (By similarity). Acetylated. Deacetylated by SIRT3. Phosphorylation at Tyr-207 is important for efficient electron transfer in complex II and the prevention of ROS generation. Belongs to the FAD-dependent oxidoreductase 2 family. FRD/SDH subfamily.