2f6e
From Proteopedia
Clostridium difficile Toxin A C-terminal fragment 1 (TcdA-f1)
Overview
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.
About this Structure
2F6E is a Single protein structure of sequence from Clostridium difficile. Full crystallographic information is available from OCA.
Reference
Crystal structure of receptor-binding C-terminal repeats from Clostridium difficile toxin A., Ho JG, Greco A, Rupnik M, Ng KK, Proc Natl Acad Sci U S A. 2005 Dec 20;102(51):18373-8. Epub 2005 Dec 12. PMID:16344467 Page seeded by OCA on Sun May 4 03:30:53 2008
