Authors

FC Caldwell¹; S Seizova¹; B Colon¹; MC Pawlowic¹;  ¹ Wellcome Centre for Anti-Infectives Research, Division of Biological Chemistry and Drug Discovery, University of Dundee, Dundee, UK, UK

Discussion

Cryptosporidium is an apicomplexan parasite and the causative agent of the diarrhoeal disease cryptosporidiosis. The parasite is waterborne and transmitted faecal-orally as an oocyst. The oocyst wall provides environmental resistance, protecting the infectious sporozoites within. The oocyst is resistant to common disinfectants (including chlorination) due to its hardy wall. It has been suggested that the cysteine-rich Cryptosporidium Oocyst Wall Proteins (COWPs) form a meshwork of disulfide bonds in the inner wall. We hypothesise that this meshwork provides the oocyst its structural strength, however it is currently unclear what catalyses the formation of these disulfide bonds. Sulfhydryl Oxidases (SOX), a highly conserved enzyme family, generally catalyse the induction of disulfide bonds, helping form higher order protein structures. A Cryptosporidium SOX, identified by a proteome from the Pawlowic Lab, has been shown to be highly expressed and enriched in the oocyst wall. I hypothesise that oxidoreductase machinery is involved in the formation of disulfide bonds in the Cryptosporidium oocyst wall, is important to crosslinking the COWPs and such contributing to the strength of the oocyst wall. Using a transgenic strain of Cryptosporidium lacking the SOX gene, I show that there is no significant reduction in disulfide bonds formed in the oocyst wall by a novel thiol assay, utilising thiol reactive probes.