The interaction of trichosanthin with supported phospholipid membranes studied by surface plasmon resonance

Trichosanthin (TCS) is a toxic protein isolated from a Chinese herbal medic ine, the root tuber of Trichosanhes kirilowii Maximowicz of the Curcurbitac eae family. It is now used in China to terminate early and mid-trimester pr egnancies. The ribosome inactivating property is thought to be account for its toxicity; it can inactivate the eukaryotic ribosome through its RNA N-g lycosidase activity. The interactions of TCS with biological membrane is th ought to be essential for its physiological effect, for it must gee across the membrane before it can enter the cytoplasm and exert its RIP function. In the present work, the interaction of TCS with supported phospholipid mon olayers is studied by surface plasmon resonance. The results show that elec trostatic forces dominate the interaction between TCS and negatively charge d phospholipid containing membranes under acid condition and that both the pH value and the ionic strength can influence its binding. It is proposed t hat, besides electrostatic forces, hydrophobic interaction may also be invo lved in the binding process. (C) 2001 Elsevier Science B.V. All rights rese rved.