Studies on mitochondria membrane proteins in Saccharomyces cerevisiae under different degrees of glucose repression

Mitochondrial membrane proteins synthesized in vivo in the presence of cycloheximide were analyzed on electrofocusing polyacrylamide gels. Five of the six protein bands observed have their isoelectric points below pH 7. The six proteins are not synthesized when both cycloheximide and chloramphenicol are present, and they are absent in a petite mutant lacking mitochondrial deoxyribonucleic acid (DNA), leading to the conclusion that the proteins are synthesized on mitochondrial ribosomes. By labeling cells of Saccharomyces cerevisiae cultivated in a chemostat under different degrees of glucose limitation, the effect of glucose repression on the synthesis of the mitochondrial membrane proteins was determined. Two of the protein bands showed a relatively reduced synthesis under the strongest glucose repression tested. The specific activity of the cytochrome oxidase and the percentage of mitochondrial DNA in the total DNA were found to be influenced at a lower level of glucose repression.