Promitochondria of anaerobically grown yeast. IV. Conversion into respiring mitochondria.

Promitochondria of anaerobically grown Saccharomyces cerevisiae were selectively labeled in vivo by incubating the cells with [(3)H]leucine and cycloheximide. When the labeled cells were washed free of cycloheximide and adapted to oxygen in the presence of unlabeled leucine, the respiring mitochondria formed during adaptation proved to be radioactive. In contrast, only insignificant label was found in iso-1-cytochrome c which is synthesized de novo during adaptation. Respiratory adaptation of anaerobically grown yeast thus involves differentiation of promitochondrial organelles.