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 (PubMed:26749241). (Microbial infection) Interacts with JC virus small t antigen. Disease susceptibility is associated with variants affecting the gene represented in this entry. The disease is caused by variants affecting the gene represented in this entry. The disease is caused by variants affecting the gene represented in this entry. The disease is caused by variants affecting the gene represented in this entry. Belongs to the succinate dehydrogenase/fumarate reductase iron-sulfur protein family.