COMPARISON OF PROPERTIES OF MISTLETOE LECTIN-I A-CHAIN AND RICIN B-CHAIN CONJUGATE WITH NATIVE TOXINS

Chimeric toxic protein was prepared from the mistletoe lectin I A-chai n and ricin B-chain by using the disulfide exchange reaction. Ricin an d chimeric protein were indistinguishable in binding to immobilized as ialofetuin in ELISA. Chimeric protein was more toxic to Jurkat cells t han native mistletoe lectin I, but not so effective as native ricin. I n the presence of NH4Cl, which enhances the toxicity of some toxins an d immunotoxins, but does not influence ricin toxicity, both ricin and chimeric toxin had equal cytotoxic activity. The possibility is discus sed that the ricin B-chain protects the ricin A-chain (RTA) from degra dation during delivering RTA from the cell surface to the place where RTA is translocated into the cytosol.