Studies on Mitochondrial Membrane Proteins in Saccharomyces cerevisiae under Different Degrees of Glucose Repression

Abstract

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.

Correlation between the rate of proteolysis of mitochondrial translation products and fluidity of the mitochondrial inner membrane in Saccharomyces cerevisiae yeast. Alteration of the rate of proteolysis under glucose repression

“…Both in control and under glucose repression, after the electrophoretic resolution of the mitochondrial translation products the highest radioactivity was detected in components with apparent Mr values of 56000, 49000, 43000, 33000, 22000, 14500, and 8000. These data are roughly the same as those of Ibrahim et al (1973) and Mian et al (1973), who found that glucose repression changes only the relative content of the individual mito-chondrially made polypeptides, with the set of these polypeptides remaining the same.…”

Lipophilic Proteins of Mitochondria from Microaerobic and Aerobic Continuous Cultures of Saccharomyces cerevisiae

“…Kadenbach and Hadvary (7), Sierra and Tzagoloff (17), and Michel and Neupert (12) have discussed the possible role of small lipophilic molecules in the synthesis and assembly of mitochondrial membranes. Previous studies showed that the nature of the membrane proteins made by the mitochondria in Saccharomyces cerevisiae is regulated by environmental factors such as oxygen tension and glucose concentration (5,11,15). Whether this control extends to the synthesis of the lipophilic proteins and, therefore, reflects fundamental changes in mitochondrial membrane structure is the subject of this communication.…”