<p>The ubiquinol-cytochrome C reductase complex (cytochrome bc1 complex) is an essential component of the mitochondrial cellular respiratory chain. This family represents the 6.4 kDa protein, which may be closely linked to the iron-sulphur protein in the complex and function as an iron-sulphur protein-binding factor [<cite idref="PUB00031170"/>]. </p>