Dithiothreitol, succinate dehydrogenase

Conditions Complex II was inactivated by 20 min incubation at pH 9.3 and readjusted to pH 7.6 (protein 11.25 mg/ml). Succinate dehydrogenase was prepared and stored as an ammonium sulfate-precipitated pellet for 1 day at —70°. It was dissolved in 50 mM Tris-HCl (pH 8.0) containing 20 mAf succinate and 5 mAf di-thiothreitol before using (protein 21.1 mg/ml). Alkali-treated complex II (0.5 ml) and succinate dehydrogenase (0.6 ml) were mixed together, assayed, and centrifuged for 60 min at 49,000 rpm. The supernatant and the pellet were then separated, the latter was suspended in Tris-succinate-dithiothreitol buffer and both fractions were assayed as indicated. Activities shown are expressed as micromoles of succinate oxidized X min X mg of total protein at. 38°. 

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