INTERACTION OF DIPHTHERIA-TOXIN FRAGMENT-A, FRAGMENT-B AND PROTEIN-CRM-45 WITH LIPOSOMES

Diphtheria toxin, its fragments A, B and the protein serologically related to toxin, crm 45, were studied for their hydrophobicity using the method of charge shift electrophoresis. These molecules were then assayed for liposome interaction. The results showed that the diphtheria toxin B fragment behaves as an amphiphatic protein because it contains a hydrophobic domain located in that portion of the B chain which remains in protein crm 45. Toxin fragment A is hydrophilic. Incubation of protein crm 45 or toxin fragment B with preformed liposomes leads to association of these proteins with lipid vesicles. Fragment A does not interact with liposomes. Binding of protein crm 45 with lipid vesicles is dependent on time and temperatue. Protein crm 45 is unidirectionally associated with liposomes, its enzymic fragment A directed outside the liposome. Fragment B or protein crm 45, upon binding with liposomes, does not affect the permeability of the vesicles.