Figure 1.

Spectrophotometric Catalytic Activity Assay of NADH:Decylubiquinone Oxidoreduction by Isolated Deactive Complex I

Assay traces comparing enzyme that had been treated by 4 mM NEM (red) with enzyme that had not been treated (green). Without the NEM treatment the deactive protein gradually reactivates, reaching its maximal rate after 150 s. The NEM treatment prevents reactivation and the background rate is only from the small proportion of active enzyme present. Experiments were carried out using 200 μM NADH, 200 μM decylubiquinone, and 0.5 μg mL⁻¹ complex I, as described in the STAR Methods.