Diphtheria Toxin CRM197: Properties, Uses & Research Guide
Diphtheria Toxin CRM197: Properties, Uses & Research Guide
Diphtheria Toxin(CRM197) is a genetically detoxified, non-toxic mutant of the native diphtheria toxin that retains full immunogenicity, making it one of the most widely adopted carrier proteins in conjugate vaccine development and biomedical research.
- Product SKU
- D381867
- Alternate Reference
- Santa Cruz sc-391135
- Protein Type
- Non-toxic single-point mutant of diphtheria toxin (Gly52 → Glu substitution in the catalytic domain)
- Key Property
- Retains full antigenicity and immunogenicity of native diphtheria toxin but lacks ADP-ribosyltransferase enzymatic activity
- Primary Applications
- Conjugate vaccine carrier, hapten conjugation, immunogenicity enhancement, cell biology research
- Regulatory Precedent
- Approved carrier protein in multiple licensed human vaccines (e.g., Prevnar 13, Menveo)
What Is CRM197? Molecular Background and Origin
CRM197 (Cross-Reacting Material 197) is a naturally occurring, non-toxic point mutant of diphtheria toxin produced by Corynebacterium diphtheriae infected with a specific bacteriophage carrying a mutated tox gene. The critical mutation—a single amino acid substitution (Glycine 52 to Glutamic acid) in the enzymatic A fragment—abolishes the protein's ADP-ribosyltransferase activity and thus its cytotoxicity, while leaving the overall three-dimensional structure and antigenicity essentially intact.
Because CRM197 and the native diphtheria toxin share near-identical epitopes, antibodies raised against CRM197 cross-react with the native toxin, providing protective immunity. This combination of safety and immunopotency makes CRM197 uniquely valuable as a carrier protein for conjugate vaccines and as a research tool protein.
Key Applications of CRM197 in Research and Vaccine Development
1. Conjugate Vaccine Development: CRM197 is the carrier protein of choice in several licensed conjugate vaccines targeting polysaccharide antigens from Streptococcus pneumoniae, Neisseria meningitidis, and Haemophilus influenzae type b. By covalently coupling poorly immunogenic polysaccharides to CRM197, T-cell-dependent immune responses are elicited, resulting in robust, long-lasting immunity including immunological memory.
2. Hapten and Small-Molecule Conjugation: CRM197 is routinely conjugated to haptens, peptides, and small molecules to render them immunogenic for antibody production or immunological assays. Its abundant lysine residues provide multiple accessible conjugation sites.
3. Cell Biology and Receptor Studies: The receptor-binding domain (B fragment) of CRM197 binds to heparin-binding EGF-like growth factor (HB-EGF) on cell surfaces. This property enables researchers to use CRM197 as a tool to study HB-EGF receptor biology, cell entry mechanisms, and EGF receptor signaling pathways.
4. Drug Delivery Research: The cell-binding activity of CRM197 has been explored in targeted drug delivery systems, where it serves as a vehicle to direct payloads to cells expressing HB-EGF.
Biochemical Properties and Handling Considerations
Molecular Weight: CRM197 has an approximate molecular weight of 58.4 kDa, consistent with the native diphtheria toxin polypeptide chain prior to proteolytic nicking.
Structure: Like the native toxin, CRM197 consists of three functional domains: the enzymatically inactive catalytic (C) domain, the transmembrane (T) domain, and the receptor-binding (R) domain. The R domain retains binding affinity for HB-EGF.
Storage and Stability: CRM197 should be stored at –20 °C or –80 °C to maintain long-term stability. Repeated freeze-thaw cycles should be avoided; aliquoting upon receipt is recommended. Reconstituted protein should be kept on ice during working sessions.
Safety: Although CRM197 is non-toxic and lacks enzymatic activity, it should be handled according to standard laboratory biosafety practices for recombinant proteins. Always consult the product SDS before use.
Note: Specific purity, concentration, and formulation data for SKU D381867 should be confirmed in the current Certificate of Analysis (CoA) available from Aladdin Scientific.
Selecting and Ordering CRM197 from Aladdin Scientific
Aladdin Scientific offers Diphtheria Toxin (CRM197) under SKU D381867 (Santa Cruz reference sc-391135). When selecting CRM197 for your application, consider the following:
- Intended Application: Vaccine research and hapten conjugation typically require high-purity, endotoxin-tested material. Confirm endotoxin levels in the CoA if your application is cell-based or in vivo.
- Lot-to-Lot Consistency: Request CoA and SDS for each lot to verify protein purity (typically assessed by SDS-PAGE), biological activity, and sterility where applicable.
- Quantity: CRM197 is available for research-scale use. Contact Aladdin Scientific for bulk or custom requirements.
- Regulatory Compliance: For GMP or clinical applications, discuss with your Aladdin Scientific representative regarding available documentation.
For pricing, availability, and technical support, please contact Aladdin Scientific customer service or visit the product page for D381867.
Frequently asked questions
Is CRM197 the same as diphtheria toxin?
CRM197 is a non-toxic mutant of diphtheria toxin bearing a single amino acid substitution (Gly52Glu) in the catalytic domain that eliminates ADP-ribosyltransferase activity and cytotoxicity. It is structurally and antigenically very similar to native diphtheria toxin but is safe to handle under standard laboratory biosafety conditions. It is not the same as the active toxin.
Why is CRM197 preferred as a carrier protein for conjugate vaccines?
CRM197 is preferred because it is highly immunogenic, well-characterized, and has an established safety and regulatory track record in multiple licensed human vaccines. Its abundant surface lysines allow efficient chemical conjugation to polysaccharides or haptens, and the resulting conjugates reliably elicit T-cell-dependent immune responses with immunological memory.
What storage conditions are recommended for CRM197 (D381867)?
CRM197 should generally be stored at –20 °C for short-term use or –80 °C for long-term storage. Avoid repeated freeze-thaw cycles by aliquoting the protein upon receipt. Always refer to the specific Certificate of Analysis (CoA) supplied with lot D381867 for confirmed storage and stability recommendations.
Can CRM197 be used for cell-based assays involving HB-EGF signaling?
Yes. CRM197 binds to heparin-binding EGF-like growth factor (HB-EGF) on the cell surface via its receptor-binding domain, making it a useful research tool for studying HB-EGF receptor interactions and downstream signaling. Researchers have employed CRM197 as a competitive inhibitor of HB-EGF to investigate EGF receptor pathways. Endotoxin levels should be verified before cell-based use.
References
- Uchida T, Pappenheimer AM Jr, Greany R. Diphtheria toxin and related proteins. I. Isolation and properties of mutant proteins serologically related to diphtheria toxin. J Biol Chem. 1973;248(11):3838-3844.
- Broker M, Berti F, Schneider J, Vojtek I. Polysaccharide conjugate vaccine protein carriers as a driver of antibody responses. Hum Vaccin Immunother. 2021;17(4):978-995.
- Bhatt S, et al. CRM197: Structure, function and conjugate vaccine applications. Vaccine. (Representative review article — specific citation details require verification).
Products are supplied for research and development use only. Not for use in humans, animals, diagnosis, or therapy.
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