The large subunit (mol wt: 65,000) of sweet potato succinate dehydrogenase was isolated by SDS-polyacrylamide gel electrophoresis of a succinate dehydrogenase preparation, which had been partially purified from root mitochondria by solubilizing the enzyme with Emulgen 810, DEAE-cellulose column chromatography, and polyacrylamide gel electrophoresis. Antibody to the purified large subunit was produced in a rabbit, and the antiserum obtained was judged to be specific to the large subunit based on the results of double immunodiffusion tests and immunoelectrophoresis. Rocket immunoelectrophoresis with the antiserum showed that the increase in succinate dehydrogenase activity during the ageing of sliced, sweet potato root tissue was due to an increase in the amount of enzyme protein. Both the increases in the activity of succinate dehydrogenase and in the amount of the large subunit protein were inhibited by cycloheximide or chloramphenicol. We propose that synthesis of the large subunit of succinate dehydrogenase on cytoplasmic ribosomes is controlled by a mitochondrial translation product(s).
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