Proton potential-dependent polyamine transport by vacuolar membrane vesicles of Saccharomyces cerevisiae

Abstract

Vacuolar membrane vesicles of Saccharomyces cerevisiae accumulated spermine and spermidine in the presence of ATP, not in the presence of ADP. Spermine and spermidine transport at pH 7.4 showed saturation kinetics with K m values of 0.2 mM and 0.7 mM, respectively. Spermine uptake was competitively inhibited by spermidine and putrescine, but was not affected by seven amino acids, substrates of active transport systems of vacuolar membrane. Spermine transport was inhibited by the H +-ATPase-specific inhibitors bafilomycin A 1 and N, N′-dicyclohexylcarbodiimide, but not by vanadate. It was also sensitive to Cu 2+ or Zn 2+ ions, inhibitors of vacuolar H +-ATPase. Both 3,5-di- tert-butyl-4-hydroxybenzilidenemalononitrile (SF6847) and nigericin blocked completely the spermine uptake, but valinomycin did not. [ 14C]Spermine accumulated in the vesicles was exchangeable with unlabeled spermine and spermidine. However, it was released by a protonophore only in the presence of a counterion such as Ca 2+. These results indicate that a polyamine-specific transport system depending on a proton potential functions in the vacuolar membrane of this organism.