2F6E

Clostridium difficile Toxin A C-terminal fragment 1 (TcdA-f1)

Summary for 2F6E

• Entry DOI: 10.2210/pdb2f6e/pdb
• Descriptor: Toxin A (2 entities in total)
• Functional Keywords: beta solenoid, c-terminal repetitive domain, crops, toxin
• Biological source: Clostridium difficile
• Total number of polymer chains: 1
• Total formula weight: 14197.85

Authors

Ng, K.K.,Ho, J.G. (deposition date: 2005-11-29, release date: 2005-12-20, Last modification date: 2024-05-29)

Primary citation

Ho, J.G.,Greco, A.,Rupnik, M.,Ng, K.K.
Crystal structure of receptor-binding C-terminal repeats from Clostridium difficile toxin A
Proc.Natl.Acad.Sci.Usa, 102:18373-18378, 2005

PubMed Abstract: Clostridium difficile is a major nosocomial pathogen that produces two large protein toxins [toxin A (TcdA) and toxin B (TcdB)] capable of disrupting intestinal epithelial cells. Both belong to the family of large clostridial cytotoxins, which are characterized by the presence of a repetitive C-terminal repetitive domain (CRD). In TcdA, the CRD is composed of 39 repeats that are responsible for binding to cell surface carbohydrates. To understand the molecular structural basis of cell binding by the toxins from C. difficile, we have determined a 1.85-A resolution crystal structure of a 127-aa fragment from the C terminus of the toxin A CRD. This structure reveals a beta-solenoid fold containing five repeats, with each repeat consisting of a beta-hairpin followed by a loop of 7-10 residues in short repeats (SRs) or 18 residues in long repeats (LRs). Adjacent pairs of beta-hairpins are related to each other by either 90 degree or 120 degree screw-axis rotational relationships, depending on the nature of the amino acids at key positions in adjacent beta-hairpins. Models of the complete CRDs of toxins A and B suggest that each CRD contains straight stretches of beta-solenoid composed of three to five SRs that are punctuated by kinks introduced by the presence of a single LR. These structural features provide a framework for understanding how large clostridial cytotoxins bind to cell surfaces and suggest approaches for developing novel treatments for C. difficile-associated diseases by blocking the binding of toxins to cell surfaces.

PubMed: 16344467
DOI: 10.1073/pnas.0506391102

Experimental method

X-RAY DIFFRACTION (1.85 Å)