The UQCRX/QCR9 protein is the 9/10 subunit of complex III, encoding a protein of about 7-kDa. Deletion of QCR9 results in the inability of cells to grow on grow on-fermentable carbon source n yeast [1].

1: QCR9, the nuclear gene encoding a small subunit of the mitochondrial cytochrome bc1 complex, maps to the right arm of chromosome VII in Saccharomyces cerevisiae. Phillips JD, Trumpower BL; Yeast 1993;9:95-97. PMID:8382892