The function of UQCC4 (ubiquinol-cytochrome c reductase complex assembly factor 4, ENSG00000174109) is as follows. Required for the assembly and stability of the mitochondrial ubiquinol-cytochrome c reductase complex (complex III (CIII) or cytochrome b-c1 complex), a multisubunit transmembrane complex that is part of the mitochondrial electron transport chain (ETC) which drives oxidative phosphorylation. .