Bovine seminal ribonuclease destabilizes negatively charged membranes.

Bovine seminal ribonuclease (BS-RNase), an antitumor protein selectively cytotoxic for malignant cells, (i) specifically aggregates negatively charged vesicles and modifies the thermotropic behaviour of the phospholipid; (ii) decreases the amplitude of the thermal transition of the phospholipid; and (iii) provokes lipid-mixing between bilayers of negatively charged vesicles. This engenders leakage of the aqueous vesicle 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 antitumor action of the protein.