Crystal structures of the GH18 domain of the bifunctional peroxiredoxin–chitinase CotE from Clostridium difficile. Issue 6 (8th June 2020) - Whittingham, Jean L.
Abstract : Clostridium difficile is a spore‐forming bacterium and a leading cause of hospital‐acquired antibiotic‐associated diarrhoea. Symptoms of disease result from secreted toxins, while disease transmission is mediated via resistant endospores. CotE is a bifunctional spore‐coat protein with peroxiredoxin and chitinase domains that are implicated in colonization. Here, the structure of the chitinase domain of CotE has been determined, revealing a GH18 family fold and, unexpectedly, a peptide bound in the active site. Abstract : CotE is a coat protein that is present in the spores of Clostridium difficile, an obligate anaerobic bacterium and a pathogen that is a leading cause of antibiotic‐associated diarrhoea in hospital patients. Spores serve as the agents of disease transmission, and CotE has been implicated in their attachment to the gut epithelium and subsequent colonization of the host. CotE consists of an N‐terminal peroxiredoxin domain and a C‐terminal chitinase domain. Here, a C‐terminal fragment of CotE comprising residues 349–712 has been crystallized and its structure has been determined to reveal a core eight‐stranded β‐barrel fold with a neighbouring subdomain containing a five‐stranded β‐sheet. A prominent groove running across the top of the barrel is lined by residues that are conserved in family 18 glycosyl hydrolases and which participate in catalysis. Electron density identified in the groove defines the pentapeptide Gly‐Pro‐Ala‐Met‐Lys derived from the N‐terminus of the protein following proteolytic cleavage to remove an affinity‐purification tag. These observations suggest the possibility of designing peptidomimetics to block C. difficile transmission.