Labyntsev A. Molecular mechanisms of diphtheria toxin receptor-binding and transporting functions

Object: mechanisms of the bacterial toxins biological activity. Objective: To establish the peculiarities of the molecular mechanisms of receptor-binding and transporting functions of diphtheria toxin. Methods: protein and DNA gel electrophoresis, metal affinity chromatography, protein and DNA cloning, spectrofluorometry, flow cytometry, confocal microscopy, cell culture of eukaryotes. It was obtained and characterized recombinant model proteins, which is necessary for studies of diphtheria toxin receptor-binding and transporting functions. The ability of diphtheria toxin fluorescent derivative to interact with the surface and penetrate inside the insensitive to the toxin mouse cells was demonstrated. It was found dose-dependent ability of diphtheria toxin subunit B to induce cell death via apoptosis of U937 cell line; this ability was not associated with the interaction with the receptor on the cell surface and the formation of large pores. It is shown that the T-domain of diphtheria toxin slows down maturation of toxin fragments loaded endosomes and inhibit acidification of their environment.