Rubescenslysin and phallolysin release marker molecules from phospholipid cholesterol liposomes

Multilamellar liposomes were prepared from phospholipid, cholesterol and dicetyl phosphate and marked with potassium chromate or with glucose. They were treated with 0.5--50 haemolytic units (HU)/ml of rubescenslysin from Amanita rubescens or of phallolysin from Amanita phalloides. Rubescenslysin caused a dose-dependent release of marker molecules from phosphatidylcholine and from sphingomyelin liposomes. A statistically significant marker leakage was caused by 0.5--1 HU/ml from liposomes prepared from sphingomyelin, phosphatidylcholine from egg yolk, and among the synthetic phosphatidylcholines from distearoyl greater than dipalmitoyl greater than dioleoyl phosphatidylcholine. With the lysin concentrations tested, at the best 50% of total markers were released from sphingomyelin liposomes and 75--95% from phosphatidylcholine liposomes. Also phallolysin released marker molecules from phosphatidylcholine liposomes; statistically significant amounts were released by 0.5 HU/ml from egg yolk phosphatidylcholine and from dipalmitoyl congruent to distearoyl greater than dioleoyl phosphatidylcholine liposomes; 60--90% of maximum release was achieved at the best. However, liposomes prepared from (bovine) sphingomyelin were resistant to phallolysin; even with 50 HU/ml no leakage of markers was observed. Heat-inactivated rubescenslysin, heat-inactivated phallolysin and human serum albumin failed to release markers. Our results lead to the conclusion that both, rubescenslysin and phallolysin, interact with membrane phospholipids, phallolysin showing a higher degree of specificity.