Repression of in vivo synthesis of the mitochondrial elongation factors T and G in Saccharomyces fragilis.

In vivo synthesis of the mitochondrial elongation factors T and G in the yeast Saccharomyces fragilis can be repressed. Enzymatic activity assays and immunochemical titration methods reveal that cells grown in the presence of 8% glucose or in the absence of oxygen contain relatively lower amounts of mitochondrial elongation factors than cells grown in the presence of lactate. In contrast, in vivo production of the cytoplasmic elongation factors 1 and 2 does not respond to such a change of extracellular conditions. The rate of growth does not affect the level of the mitochondrial elongation factors. Production of both enzymes is almost constant during logarithmic growth, but decreases when the stationary phase is reached. Chloramphenicol, an inhibitor of mitochondrial protein synthesis, does not block but, rather, seems to enhance the in vivo synthesis of mitochondrial T or G.