Change in P-450 Content Accompanying Aerobic Formation of Mitochondria in Yeast

The content of P-450, a CO-binding hemoprotein, in wild-type yeast cells grown anaerobically decreased sharply on exposure to aerobic conditions. This change paral-leled the formation of mitochondria within the cells. High concentrations of glucose and chloramphenicol inhibited both the decrease in P-450 and the development of mito-chondrial type of respiration. A similar decrease in P-450 was also observed when cells of a semi-anaerobically grown respiration-deficient mutant were aerated. The weak respiration of anaerobically and semi-anaerobically grown wild-type yeast and semi-anaerobically grown mutant yeast cells was insensitive to antimycin A. The rate of this insensitive respiration was proportional to the content of P-450 in various types of cells. Possible relationships between P-450 and mitochondrial synthesis are discussed. Exposure of anaerobically grown cells of yeast to air induces rapid synthesis of mito-chondria without accompanying cell prolifera-tion (1). Concomitant with this synthesis, respiratory activity of the cells increases pro