Development of a novel molecular adapter for the optimization of immunotoxins

Immunotoxins consisting of catalytic domains of natural toxins and tumor-sp ecific ligands were modified by introducing a molecular adapter that is abl e to transport the toxic domain more efficiently into cells. The adapter is a three-component structure: its core is a membrane transfer sequence (NIT S) flanked by two different cleavable sequences. The directed and irreversi ble cellular uptake of the construct is driven by either enzymatic or chemi cal cleavage of the two flanking sequences. In our studies, the purified A- chain of diphtheria toxin (DT) was coupled to two different MTSs via disulf ide bonds. A cytotoxicity assay revealed that the constructs containing the MTSs were more potent than DT A-chain alone and that the disulfide bond wa s cleaved. (C) 2001 Elsevier Science B.V. Ali rights reserved.