Component of the ubiquinol-cytochrome c reductase complex (complex III or cytochrome b-c1 complex that is part of the mitochondrial respiratory chain. The b-c1 complex mediates electron transfer from ubiquinol to cytochrome c. Contributes to the generation of a proton gradient across the mitochondrial membrane that is then used for ATP synthesis.,MTCYB,MT-CYB,Signal Transduction,Endocrine & Metabolism,Mitochondrial metabolism,Cytochromes,Neuroscience,Neurodegenerative Diseases,MT-CYB