Members of this family adopt a structure consisting of many antiparallel beta sheets, with few alpha helices, in a non-globular arrangement. They are required for proper functioning of the respiratory chain [1].

1: The crystal structure of mitochondrial cytochrome bc1 in complex with famoxadone: the role of aromatic-aromatic interaction in inhibition. Gao X, Wen X, Yu C, Esser L, Tsao S, Quinn B, Zhang L, Yu L, Xia D; Biochemistry. 2002;41:11692-11702. PMID:12269811