Ubiquitin cytochrome c reductase UQCRFS1 is a key subunit of cytochrome BC1 complex (complex III) in the mitochondrial respiratory chain, involved in the components of mitochondrial respiratory chain complex III and respiratory electron transport chain. It may participate in the more aggressive breast cancer phenotype. The transport peptide of Rieske protein appears to be part of the BC1 complex and is believed to be subunit 11/IX.
