Nucleic acids and protein synthesis in cancer cell mitochondria. II. Amino acid incorporation into proteins of rat liver and hepatoma cell mitochondria

The energy source required for the amino acid incorporation into mitochondrial proteins has been investigated and comparative study has also been made on the rate of the amino acid incorporation in rat liver and rat hepatoma cell mitochondria. 1. The incorporation of amino acid into the protein in intact mitochondria of rat liver increased by about 40% on the addition of α-ketoglutarate and ADP, but no significant increase in the amino acid incorporation was observed on the addition of succinate and ADP. 2. The incorporation of amino acids into mitochondrial proteins was remarkably inhibited by the addition of respiratory inhibitors (cyanide, DNP at a high concentration). 3. The amino acid incorporation into mitochondrial proteins was scarcely or slightly inhibited by the addition of DNP at the concentration of 1×10-4M and insensitive to oligomycin (5 to 10 μg/ml). 4. The amino acid incorporation into the protein in the endogenous substrate system of the mitochondria was considerably inhibited by the addition of arsenite, and this inhibition somewhat recovered on the addition of ADP plus succinate. 5. The rate of the amino acid incorporations between rat liver and hepatoma cell mitochondria was at the same level. 6. Discussions were made on the energy source required for the amino acid incorporation into mitochondrial proteins, on the rate of protein synthesis per mitochondrion isolated from rat liver- and hepatoma cells, and on the possibilities of contamination of bacteria or microsomes and of the adsorption of amino acids onto the mitochondria.