a menaquinone + succinate = a menaquinol + fumarate Binds 1 [2Fe-2S] cluster. Binds 1 [3Fe-4S] cluster. Binds 1 [4Fe-4S] cluster. Part of an enzyme complex containing three subunits: a flavoprotein (frdA), an iron-sulfur protein (frdB), and diheme cytochrome b (frdC). Belongs to the succinate dehydrogenase/fumarate reductase iron-sulfur protein family.