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Clostridium difficile is a burden to healthcare systems around the world, causing tens of thousands of deaths annually. The S-layer of the bacterium, a layer of protein found of the surface of cells, has received a significant amount of attention over the past two decades as a potential target to combat the growing threat presented by C. difficile infections. The S-layer contains a wide range of proteins, each of which possesses three cell wall-binding domains, while many also possess a 'functional' region. Here, we present the high resolution structure of the functional region of one such protein, Cwp19 along with preliminary functional characterisation of the predicted glycoside hydrolase. Cwp19 has a TIM barrel fold and appears to possess a high degree of substrate selectivity. The protein also exhibits peptidoglycan hydrolase activity, an order of magnitude slower than that of lysozyme and is the first member of glycoside hydrolase-like family 10 to be characterised. This research goes some way to understanding the role of Cwp19 in the S-layer of C. difficile. Database Structural data are available in the PDB under the accession numbers and . [ABSTRACT FROM AUTHOR]

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 1.9Å, 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. [ABSTRACT FROM AUTHOR]