(A) Mitochondrial extracts from 143B cells, COX1∆ and COX2∆ mutant cybrids and their respective isogenic controls (CON-1 and CON-2) were analyzed by SDS-PAGE and immunoblotting with the indicated antibodies. The graphs (right) show densitometric quantifications of the signals normalized to CII subunit SDHA. The mean of three independent controls (CON) was set to 100 and all measurements were referenced to that value. The values represent mean ± SD (n=3-8). Mann-Whitney U test was applied for statistical analyses. Variations between controls and mutants: α, p<0.05; β, p<0.01; γ, p<0.001. Specific variations between COX1∆ and COX2∆ mutants: ∗p<0.05; ∗∗p<0.01. 