Iron-sulfur protein (IP) subunit of the succinate dehydrogenase complex (mitochondrial respiratory chain complex II), responsible for transferring electrons from succinate to ubiquinone (coenzyme Q). a quinone + succinate = a quinol + fumarate Binds 1 [2Fe-2S] cluster. Binds 1 [3Fe-4S] cluster. Binds 1 [4Fe-4S] cluster. 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 SDHAF1; the interaction is required for iron-sulfur cluster incorporation into SDHB (By similarity). Belongs to the succinate dehydrogenase/fumarate reductase iron-sulfur protein family.