Catalyzes fumarate reduction using artificial electron donors such as methyl viologen. The physiological reductant is unknown, but evidence indicates that flavocytochrome c participates in electron transfer from formate to fumarate and possibly also to trimethylamine oxide (TMAO). This enzyme is essentially unidirectional. a quinone + succinate = a quinol + fumarate Binds 1 FAD per subunit. Monomer. By anaerobiosis and fumarate. In the C-terminal section; belongs to the FAD-dependent oxidoreductase 2 family. FRD/SDH subfamily. The N-terminal sequence has been extracted from PDB entry 1LJ1.