Mistletoe lectin A-chain unfolds during the intracellular transport

Protein conformation during intracellular routing and translocation of the ribosome-inactivating proteins was investigated on hybridomas producing mon oclonal antibodies (monAbs) against mistletoe lectin (ML), Decrease in the toxin activity towards these hybridomas is accounted for by the intracellul ar interaction of monAbs and the toxin resulting in the interruption of enz ymatic subunit translocation into the cytosol, Obtained monAbs interacted w ith denatured ML A-chain (MLA) and a panel of MLA synthetic octapeptides li nked to the surface of polyethylene pins. Enzyme-linked immunosorbent assay (ELISA) shows that monAbs recognize five epitopes in denatured MLA. Treatm ent of MLA by 3 M of guanidine hydrochloride leads to appearance of the epi topes, Hybridoma TA7 has been shown to be insensitive to cytotoxic action o f ML. TA7 monAb as we have shown recognizes epitope 101-105, FTGTT, and inh ibits the liposome aggregation induced by MLA, A study of the cytotoxicity of ML and ricin for the hybridomas revealed that the unfolding of A-chain i s probably required for intracellular transport and cytotoxic activity of M L, (C) 1999 Federation of European Biochemical Societies.