crm197 protein

CRM197 is a non-toxic mutant of diphtheria toxin, currently used as a carrier protein for polysaccharides and haptens to make them immunogenic. CRM197 is a genetically detoxified form of diphtheria toxin. A single mutation at position 52, substituting glutamic acid for glycine, causes the ADP-ribosyltransferase activity of the native toxin to be lost. CRM197 is widely used as a carrier protein for conjugate vaccines, because it is genetically detoxified and retains its full complement of lysine amines for conjugation. There is also evidence suggesting that, compared with tetanus toxoid, there is less carrier-induced suppression of the immune response, especially when there are many individual polysaccharides linked to the same carrier protein.