PROTEIN-SYNTHESIS BY ISOLATED PEA MITOCHONDRIA IS DEPENDENT ON THE ACTIVITY OF RESPIRATORY COMPLEX-II

In isolated pea (Pisum sativum L.) mitochondria incorporation of S-35- methionine into newly synthesised proteins was influenced by the prese nce of site-specific inhibitors of the respiratory electron-transport chain. These effects were not produced by changes in the rate of respi ratory electron transport itself nor by changes in ATP concentration. Protein synthesis was inhibited by inhibitors of ubiquinone reduction but not by inhibitors of ubiquinol oxidation. By the use of additional inhibitors at specific sites of the respiratory chain, different oxid ation-reduction states were obtained for the different complexes in th e electron-transport chain. It was found that electron transport throu gh succinate:ubiquinone oxidoreductase (respiratory complex II) was sp ecifically required for protein synthesis, even when all the other con ditions for protein synthesis were satisfied. We suggest that a subuni t of complex II, or a component closely associated with complex II, is involved in a regulatory system that couples electron transport to pr otein synthesis.