Evidence for three different electrophoretic pathways in yeast mitochondria: ion specificity and inhibitor sensitivity.

We identified three electrophoretic pathways by spectrophotometrically following the swelling of isolated yeast mitochondria: An anion uniport whose activity could only be detected after depletion of divalent cations from the matrix by treatment with 1,10-phenanthroline. This uniport was inhibited by Mg2+ and dicyclohexylcarbodiimide. A K+ (Na+) uniport which was detected only when mitochondria were suspended at low pH and low temperature. This uniport was sensitive to ruthenium red and oleic acid. A K+ selective uniport which was activated by alkaline pH and ATP depletion. This pathway was sensitive to glibenclamide and to various amphiphilic cations. Similarities and differences between these three electrophoretic pathways and the electrophoretic systems described in mammalian and plant mitochondria are discussed.