INVESTIGATION OF THE YEAST MITOCHONDRIAL UNSELECTIVE CHANNEL IN INTACT AND PERMEABILIZED SPHEROPLASTS

The existence of an activity corresponding to the nucleotide-induced Y east Mitochondria Unselective Channel (YMUC2) of isolated mitochondria was investigated in permeabilized and intact spheroplasts of the bake r's yeast Yeast Foam. In nystatin-permeabilized spheroplasts, ATP and GDP-beta-S induced a decavanadate-sensitive stimulation of the respira tion only under conditions equivalent to those previously reported for isolated mitochondria (low phosphate concentration, presence of a sal t). On Intact spheroplasts, parallel measurements of respiration rate, [ATP]/[ADP] ratio and mitochondrial transmembrane potential allowed t o show that the addition of the glucose analog 2-deoxyglucose decrease d the permeability of the inner mitochondrial membrane owing to cellul ar ATP depletion. This strongly supports the hypothesis that Yeast Mit ochondria Unspecific Channel is active in situ and inhibited by cellul ar [ATP] depletion.