RELEASE OF CYTOCHROME-C AND DECREASE OF CYTOCHROME-C-OXIDASE IN BAX-EXPRESSING YEAST-CELLS, AND PREVENTION OF THESE EFFECTS BY COEXPRESSIONOF BCL-X(L)

The characteristics of mitochondria of yeast cells expressing the pro- apoptotic gene Bar or coexpressing Bar and the anti-apoptotic gene Bcl -x(L) have been investigated in whole cells, isolated mitochondria and permeabilized spheroplasts, It is found that Bar-induced growth arres t of yeast cells is related to two defects in the respiratory chain: ( i) a decrease in the amount of cytochrome c oxidase, the terminal enzy me of the respiratory chain, and (ii) a dramatic increase in the relea se of cytochrome c to the cytosol. Other components of the inner mitoc hondrial membrane (bc(1) complex and F0F1-ATPase) are unaffected. Coex pression of Bcl-x(L) almost fully prevented the effect of Bax. Surpris ingly, these results obtained in yeast parallel similar observations r eported in mammalian cells, (C) 1997 Federation of European Biochemica l Societies.