Effect of D (minus)- and L (plus)-threo-chloramphenicol on nucleotide and related respiratory activities in yeast undergoing metabolic repression and de-repression

Effect of temperature on protein synthesis and leucine transport by yeast mitochondria

Protein synthesis in yeast mitochondria shows biphasic Arrhenius plots both in vivo and in vitro, with a twofold increase in the activation energy below the transition temperature suggesting a functional association between mitochondrial protein synthesis and the inner membrane. Analysis by gel electrophoresis of mitochondrial translation products labeled in vivo showed that the same proteins are synthesized and then inserted into the membrane above and below the transition temperature of the membrane. The rate of leucine uptake into mitochondria was decreased at least fivefold in the presence of chloramphenicol, suggesting that leucine is used mainly for protein synthesis. In the absence of chloramphenicol, the rate of leucine uptake was always slightly higher but comparable to the incorporation rate of leucine into protein at all temperatures studied, suggesting that the transport of leucine into mitochondria is not rate-limiting for protein synthesis. The ionophore valinomycin or the uncoupler carbonyl phenylhydrazone (CCCP) inhibited 75-80% of the leucine uptake in the presence of chloramphenicol. In addition, the omission of respiratory chain substrates and the ATP-regenerating system led to a 93% inhibition of uptake, suggesting that leucine uptake may occur by an active transport mechanism.

Mitochondrial biogenesis in cultured animal cells. I. Effect of chloramphenicol on morphology and mitochondrial respiratory enzymes

The effects of chloramphenicol on the morphology and respiratory enzymes of BHK-21 cells in spinner culture have been examined with time. Cells treated with chloramphenicol double twice before growth ceases; these cells have increased size as measured by several techniques. Mitochondria are enlarged and appear to degenerate with prolonged treatment. Cytochrome c oxidase and succinate cytochrome c reductase activities are reduced while there is no decrease in the activities of monoamine oxidase, glutamate dehydrogenase or NADPH-cytochrome c reductase. Cytochromes aa3 and b disappear on treatment while cytochromes c + c1 appears to be unaffected. All these effects are reversible if chloramphenicol is removed within a limited period of time.

Characterization of insoluble protein fractions of mitochondria from Saccharomyces cerevisiae

Saccharomyces cerevisiae was grown in a chemostat in the presence of excess oxygen. Cells harvested from fully derepressed and strongly repressed steady states show typical promitochondria-like structures under conditions of strong repression. Insoluble membrane proteins were extracted from highly purified mitochondria and submitted to isoelectric focusing in 6% polyacrylamide gels. Some 20 protein bands were obtained from derepressed cells. The pattern was clearly different (quantitatively and possibly qualitatively) from repressed mitochondria. In contrast to ribosomal proteins, insoluble membrane protein fractions were found in the acid section (pH 4 to 6.8) of the ampholyte gels. It can be concluded that glucose repression plays a prominent role in the synthesis of the functional mitochondrial membranes.