| Abstract: | The role of the hydrophobic region of diphtheria toxin B moiety in fragment A membrane traversal has been studied using crm45. This molecule, a serologically related diphtheria toxin protein, contains a normal enzymic fragment A and the hydrophobic domain of the toxin B chain but lacks a C-terminal polypeptide needed for specific cell binding. Relatively high concentrations of crm45 are required to inhibit protein synthesis in cells however, after the loss of its hydrophobic region crm45, which still contains an active fragment A, becomes almost non-toxic. It seems thus that the non-polar peptide found in crm45 or toxin facilitates the transport of the hydrophilic fragment A across the plasma membrane. |
