Structure of the claudin-binding domain of Clostridium perfringens enterotoxin.

Abstract

Clostridium perfringens enterotoxin is a common cause of food-borne and antibiotic-associated diarrhea. The toxin's receptors on intestinal epithelial cells include claudin-3 and -4, members of a large family of tight junction proteins. Toxin-induced cytolytic pore formation requires residues in the NH(2)-terminal half, whereas residues near the COOH terminus are required for binding to claudins. The claudin-binding COOH-terminal domain is not toxic and is currently under investigation as a potential drug absorption enhancer. Because claudin-4 is overexpressed on some human cancers, the toxin is also being investigated for targeting chemotherapy. Our aim was to solve the structure of the claudin-binding domain to advance its therapeutic applications. The structure of a 14-kDa fragment containing residues 194 to the native COOH terminus at position 319 was solved by x-ray diffraction to a resolution of 1.75A. The structure is a nine-strand beta sandwich with previously unappreciated similarity to the receptor-binding domains of several other toxins of spore-forming bacteria, including the collagen-binding domain of ColG from Clostridium histolyticum and the large Cry family of toxins (including Cry4Ba) of Bacillus thuringiensis. Correlations with previous studies suggest that the claudin-4 binding site is on a large surface loop between strands beta8 and beta9 or includes these strands. The sequence that was crystallized (residues 194-319) binds to purified human claudin-4 with a 1:1 stoichiometry and affinity in the submicromolar range similar to that observed for binding of native toxin to cells. Our results provide a structural framework to advance therapeutic applications of the toxin and suggest a common ancestor for several receptor-binding domains of bacterial toxins.

• Authors: Christina M Van Itallie, Laurie Betts, James G Smedley 3rd, Bruce A McClane, James M Anderson
• Journal: The Journal of biological chemistry (J Biol Chem) Vol. 283 Issue 1 Pg. 268-274 (Jan 04 2008) ISSN: 0021-9258 [Print] United States
• PMID: 17977833 (Publication Type: Journal Article, Research Support, N.I.H., Extramural)

Chemical References

• Bacterial Proteins
• CLDN4 protein, human
• Claudin-4
• Enterotoxins
• Membrane Proteins
• enterotoxin, Clostridium

Topics

• Amino Acid Sequence
• Bacterial Proteins (chemistry, genetics, metabolism)
• Binding Sites
• Claudin-4
• Clostridium perfringens (metabolism)
• Enterotoxins (chemistry, genetics, metabolism)
• Humans
• Membrane Proteins (chemistry, genetics, metabolism)
• Molecular Sequence Data
• Protein Binding
• Protein Structure, Secondary
• Protein Structure, Tertiary
• Structural Homology, Protein
• X-Ray Diffraction