BOVINE SEMINAL RIBONUCLEASE DESTABILIZES NEGATIVELY CHARGED MEMBRANES

Bovine seminal ribonuclease (BS-RNase), an antitumor protein selective ly cytotoxic for malignant cells, (i) specifically aggregates negative ly charged vesicles and modifies the thermotropic behaviour of the pho spholipid; (ii) decreases the amplitude of the thermal transition of t he phospholipid; and (iii) provokes lipid-mixing between bilayers of n egatively charged vesicles. This engenders leakage of the aqueous vesi cle contents. Monomeric BS-RNase, devoid of antitumor action, does not produce these effects. These results suggest that the destabilization of the membrane bilayer promoted by BS-RNase may be involved in the a ntitumor action of the protein. (C) 1994 Academic Press, Inc.