Membrane-anchoring subunit of succinate dehydrogenase (SDH). Carbohydrate metabolism; tricarboxylic acid cycle. Component of complex II composed of eight subunits in plants: four classical SDH subunits SDH1, SDH2, SDH3 and SDH4 (a flavoprotein (FP), an iron-sulfur protein (IP), and a cytochrome b composed of a large and a small subunit.), as well as four subunits unknown in mitochondria from bacteria and heterotrophic eukaryotes. Expressed in flowers, inflorescences and stems.