Figure 3.

Defective stability and activity of complex I. A, in-gel activity of complexes I, II, and IV. Twenty micrograms of mitochondrial proteins from various mutant and control cell lines was used for BN-PAGE, and the activities of complexes were measured in the presence of specific substrates (NADH and NTB for complex I, sodium succinate, phenazine methosulfate, and NTB for complex II, and DAB and cytochrome c for complex IV). B, quantification of in-gel activities of complexes I, II, and IV. The calculations were based on three independent determinations in each cell line. C–F, Enzymatic activity of respiratory chain complexes. The activities of respiratory complexes I, II, III, and IV were investigated by enzymatic assay on complex I (C), II (D), III (E), and IV (F) in mitochondria isolated from various cell lines. The calculations were based on three independent determinations. Graph details and symbols are explained in the legend to Fig. 1.