Effect of phospholipid on trichosanthin adsorption at the air-water interface

Trichosanthin (TCS) is a toxic protein with multiple pharmacological proper ties. It belongs to the type I ribosome inactivating protein (RIP) family a nd can inactivate the eukaryotic ribosome through its RNA N-glycosidase act ivity. The interaction between TCS and phospholipid membrane was thought to be essential for its physiological effect, for it must get across the cell membrane before it can enter the cytoplasm and exert its RIP function. In order to study the TCS-phospholipid interaction, the difference between spo ntaneous and phospholipid induced adsorption of TCS at the air-water interf ace was investigated, and the results were analyzed according to the diffus ion-penetration-rearrangement adsorption model. The results showed that bot h negatively charged 1,2-dipalmitoyl-sn-glycero-3-phosphoglycerol (DPPG) an d neutral 1,2-dipalmitoyl-sn-glycero-3-phosphocholine can accelerate the ad sorption rate, while there exists a possible membrane induced conformationa l change of TCS which is specific for the negatively charged DPPG. We also proposed a revised model for the diffusion controlled initial adsorption pe riod. (C) 2001 Elsevier Science B.V. All rights reserved.