MODULATION OF THE ELECTROPHORETIC ATP-INDUCED K-TRANSPORT IN YEAST MITOCHONDRIA BY DELTA-PH()

The modulation of the ATP-induced K+-transport pathway of the rast inn er mitochondrial membrane by Delta pH was investigated in two ways. Fi rst. the inhibitory effect of phosphate was compared to the effect of other permeant acids, demonstrating that a part of the effect of phosp hate was linked to its electroneutral transport down Delta pH. However , an additional effect specific for phosphate also occured inside the matrix. Second, the stimulation of the respiration by ATP in the prese nce of K+ was compared to the effects of the protonophore ClCCP2 and o f the K+-ionophore valinomycin. Quite unexpectedly, the effect of ATP looked mon like the effect of ClCCP than the effect of valinomycin. Th is and previous results (Manon cl al., Biochimica et Biophysica Acta 1 231, 282-288 (1995)) show that the rate of electrophoretic K+-entry is limited by the rate of electroneutral K+-exit via the K+-H+ exchange and is therefore Delta pH-dependent.