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 (p H 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.