Active Diphtheria toxin

Page 1170 (Figure 28 5) is adapted from crystallographic coordinates deposited with the Protein Data Bank PDB ID IDDN White A Ding X Vanderspek J C Murphy J R Ringe D Structure of the Metal Ion Activated Diphtheria Toxin Re pressor/Tox Operator Complex Nature 394 p 502 (1998)... 

White A, Ding X, vander Spek JC, Murphy JR, Ringe D. Structure of the metal-ion-activated diphtheria toxin repressor/tox operator complex. Nature 1998 394 502-506. 

Stenmark H, Afanasiev BN, Ariansen SA, Olsnes S (1992) Reconstitution of active diphtheria toxin and its fusion proteins from separate A- and B-fragments. Bio-cbemJ281 619-625. 

Microbial toxins such as diphtheria toxin and activated serum complement components can produce large pores in cellular membranes and thereby provide macromolecules with direct access to the internal miheu. 

In the early 1900s, a balanced mixture of diphtheria toxin and antitoxin was found to produce active immunity in both animals and humans. This preparation gained widespread acceptance and protected approximately 85% of recipients. Several years later, diphtheria toxoid was developed by treating the toxin with small amounts of formalin. This process caused the toxin to lose its toxic properties while maintaining its immunogenic properties. In the mid-1920s, the addition of an alum precipitate enhanced the immunogenic properties of the toxoid. 

Denileukin diftitox is a combination of the active sections of interleukin 2 and diphtheria toxin. It binds to high-affinity interleukin 2 receptors on the cancer cell (and other cells), and the toxin portion of the molecule inhibits protein synthesis to result in cell death. The pharmacokinetics of denileukin diftitox are best described by a two-compartment model, with an a half-life of 2 to 5 minutes and a terminal half-life of 70 to 80 minutes. Denileukin diftitox is used for the treatment of persistent or recurrent cutaneous T-cell lymphoma whose cells express the CD25 receptor. Side effects include vascular leak syndrome, fevers/chills, hypersensitivity reactions, hypotension, anorexia, diarrhea, and nausea and vomiting. 

Collier, R.J., and Cole, H.A. (1969) Diphtheria toxin subunit active in vitro. Science 164, 1179. 

Colliei R.J., and Kandel, J. (1971) Structure and activity of diphtheria toxin./. Biol. Chem. 246, 1496-1503. 

Colombatti, M., Greenfield, L., and Youle, R.J. (1986) Cloned fragment of diphtheria toxin linked to T cell-specific antibody identifies regions of B chain active in cell entry./. Biol. Ghem. 261, 3030. 

Oeltmann, T.N. (1985) Synthesis and in vitro activity of a hormone-diphtheria toxin fragment A hybrid. Biochem. Biophys. Res. Comm. 133, 430. 

A third type of bacterial toxin, diphtheria toxin, catalyzes the ADP-ribosylation of eukaryotic elongation factor (EFTU), a type of small G protein involved in protein synthesis (Table 19-2). The functional activity of the elongation factor is inhibitedby this reaction. Finally, a botulinum toxin ADP-ribosylates and disrupts the function of the small G protein Rho, which appears to be involved in assembly and rearrangement of the actin cytoskeleton (Table 19-2). These toxins maybe involved in neuropathy (see Ch. 36) and membrane trafficking (see Ch. 9). 

Proleukin is a recombinant form of IL-2. It is approved for the treatment of malignant melanoma and renal cell cancer. Ontak (denileukin diftitox) is a fusion protein for the treatment of persistent or recurrent T-cell lymphoma. Activated T cells express lL-2 receptors. Ontak has a fragment that binds to the IL-2 receptor while the other part presents a diphtheria toxin to kill the activated T cell. 

Classical bacterial exotoxins, such as diphtheria toxin, cholera toxin, clostridial neurotoxins, and the anthrax toxins are enzymes that modify their substrates within the cytosol of mammalian cells. To reach the cytosol, these toxins must first bind to different cell-surface receptors and become subsequently internalized by the cells. To this end, many bacterial exotoxins contain two functionally different domains. The binding (B-) domain binds to a cellular receptor and mediates uptake of the enzymatically active (A-) domain into the cytosol, where the A-domain modifies its specific substrate (see Figure 1). Thus, three important properties characterize the mode of action for any AB-type toxin selectivity, specificity, and potency. Because of their selectivity toward certain cell types and their specificity for cellular substrate molecules, most of the individual exotoxins are associated with a distinct disease. Because of their enzymatic nature, placement of very few A-domain molecules in the cytosol will normally cause a cytopathic effect. Therefore, bacterial AB-type exotoxins which include the potent neurotoxins from Clostridium tetani and C. botulinum are the most toxic substances known today. However, the individual AB-type toxins can greatly vary in terms of subunit composition and enzyme activity (see Table 2). 

C. botulinum toxins belong to the AB group of toxins, which also includes diphtheria toxin, pseudomonas exotoxin A, anthrax toxin, Shiga(like) toxin, cholera toxin, pertussis toxin, and plant toxins, e.g., ricin. Moiety A has an enzymatic activity and usually modified cellular-target entering cytosol. Moiety B consists of one or more components and binds the toxin to surface receptors, and is responsible for translocation of the A component into cells. AB toxins are produced in a non-active form and are activated by a split between two cysteine residues within a region (Falnes and Sandvig, 2000). 

Diphtheria vaccine Diphtheria toxoid formed by treating diphtheria toxin with formaldehyde Active immunization against diphtheria... 

A. General description Denileukin dif-titox is a recombinant, DNA-derived, interleukin-2 receptor specific ligand, cytotoxic fusion protein consisting of diphtheria toxin fragments A and B fused to interleukin-2. It is produced by expression of a recombinant fusion protein in Escherichia coli that contains nucleotide sequences for human interleukin-2, and sequences for the enzymatically active fragment A of diphtheria toxin and the membrane-translocating portion of diph-... 

Research also has indicated that E. coli and diphtheria toxin perform in a similar manner. Active research programs currently are being conducted at Harvard University and the University of California, Los Angeles. 

Collier, R. J., and Cole, H. A. (1969) Diphtheria toxin subunit active in vitro. Science 164,1179. Collier, R. J., and Kandel, J. (1971) Structure and activity of diphtheria toxin. J. Biol. Chem. 246, 1496-1503. 

---