Cwp2 from Clostridium difficile exhibits an extended three domain fold and cell adhesion in vitro

Colonization of the gut by Clostridium difficile requires the adhesion of the bacterium to host cells. A range of cell surface located factors have been linked to adhesion including the S-layer protein LMW SLP and the related protein Cwp66. As well as these proteins, the S-layer of C. difficile may contain many others. One such protein is Cwp2. Here, we demonstrate the production of a C. difficile strain 630 cwp2 knockout mutant and assess the effect on the bacterium. The mutant results in increased TcdA (toxin A) release and impaired cellular adherence in vitro. We also present the extended three domain structure of the 'functional' region of Cwp2, consisting of residues 29-318 at 1.9 angstrom, which is compared to that of LMW SLP and Cwp8. The adhesive properties of Cwp2 and LMW SLP, which are likely to be shared by Cwp8, are predicted to be mediated by the variable loop regions in domain 2. Databases Structural data are available in the PDB under the accession number 5NJL.