Component of the ubiquinol-cytochrome c reductase complex (complex III or cytochrome b-c1 complex), which is a respiratory chain that generates an electrochemical potential coupled to ATP synthesis. a quinol + 2 Fe(III)-[cytochrome c](out) = a quinone + 2 Fe(II)-[cytochrome c](out) + 2 H(+)(out) Binds 1 [2Fe-2S] cluster per subunit. The main subunits of complex b-c1 are: cytochrome b, cytochrome c1 and the Rieske protein. The Rieske protein is a high potential 2Fe-2S protein. Belongs to the Rieske iron-sulfur protein family.