Diphtheria toxin mutant CRM197 protein (None)

CRM197 is a genetically detoxified, non-toxic mutant of diphtheria toxin, used primarily as a carrier protein in conjugate vaccines to enhance immunogenicity of polysaccharides and haptens. It is produced by a single amino acid substitution: glycine at position 52 is replaced with glutamic acid (G52E), which abolishes the ADP-ribosyltransferase activity responsible for toxicity. The protein has a molecular mass of approximately 58–58.4 kDa and consists of 535 amino acids in a single polypeptide chain, structurally similar to native diphtheria toxin but functionally inactive as an enzyme. It is also investigated as an HB-EGF inhibitor in cancer therapy.

Converts T-independent antigens into T-dependent forms via covalent linkage; inhibits HB-EGF signaling