Protein synthesis in mitochondria

• 1.

  1. A procedure for preparing rat-liver mitochondria including a pre-incubation with RNAase (EC 2.7.7.16) to inactivate the microsomal system for amino acid incorporation is described.

• 2.

  2. The inhibition of the incorporation of amino acids into mitochondrial protein by adding substrate is correlated with a lowering of the NADP⁺/NADPH ratio.

• 3.

  3. It is shown that ammonia can relieve the inhibition by α-oxoglutarate or isocitrate of the incorporation into liver mitochondria, that this effect is not due to the glutamate formed, and that this is correlated with oxidation of NADPH to NADP⁺.

• 4.

  4. The role of endogenous substrate is discussed. It is concluded that in the case of rat-liver mitochondria α-oxoglutarate plus ammonia give the best conditions for providing energy for incorporation, since a high NADP⁺/NADPH ratio is also assured.

• 5.

  5. Judged by the effects of oligomycin and 2,4-dinitrophenol on the amino acid incorporation into protein by mitochondria, the possibility is discussed whether and in how far the high-energy intermediates of oxidative phosphorylation can meet the energy requirements for the incorporation process.