Cystamine transport in spheroplasts of Saccharomyces cerevisiae.

This work is the first demonstration that cystamine is actively accumulated in spheroplasts of Saccharomyces cerevisiae. We have identified and quantitatively determined the transported cystamine in extracts of spheroplasts that have been incubated over different time periods and in the presence of different amounts of cystamine. The method used, already reported in literature for the identification of natural aliphatic polyamines in biological fluids, consists of a derivatization of spheroplast extracts with dabsyl-chloride and subsequent chromatographic analysis in HPLC. Our results show that cystamine accumulation is a function of time, it increases up to 2.5 min then decreases. Transport is inhibited by natural aliphatic polyamines, which, at the same concentration of cystamine (1 mM), cause a decrease in cystamine transport of about 90% for spermidine, 50% for spermine and only 15% for putrescine. Furthermore, transport is energy-dependent as demonstrated by a significant decrease observed in the presence of 2,4-dinitrophenol, ouabain and vanadate. In particular 0.2 mM ouabain causes a decrease of more than 60% in cystamine transport. Our data suggest that cystamine is transported in Saccharomyces cerevisiae spheroplasts via the same polyamine transport system(s) known to be operating in higher eukaryotic cells.