The diphtheria toxin precursor is a protein of molecular weight 60 kDa. Certain proteases, such as trypsin, selectively cleave DT to generate two peptide chains, amino-terminal fragment A (DT-A) and carboxyl-terminal fragment B (DT-B), which are held together by a disulfide bond. DT-B is a recognition subunit that gains entry of DT into the host cell by binding to the EGF-like domain of heparin-binding EGF-like growth factor on the cell surface. This signals the cell to internalize the toxin within an endosome via receptor-mediated endocytosis. Inside the endosome, DT is split by a trypsin-like protease into DT-A and DT-B. The acidity of the endosome causes DT-B to create pores in the endosome membrane, thereby catalysing the release of DT-A into the cytoplasm.
The diphtheria toxin precursor is a protein of molecular weight 60 kDa Certain proteases such as trypsin selectively cleave DT to generate two peptide chains amino-terminal fragment A (DT-A) and carboxyl-terminal fragment B (DT-B) which are held together by a disulfide bond DT-B is a recognition subunit that gains entry of DT into the host cell by binding to the EGF-like domain of heparin-binding EGF-like growth factor on the cell surface This signals the cell to internalize the toxin within an endosome via receptor-mediated endocytosis Inside the endosome DT is split by a trypsin-like protease into DT-A and DT-B The acidity of the endosome causes DT-B to create pores in the endosome membrane thereby catalysing the release of DT-A into the cytoplasm