Abstract
Background C. pseudotuberculosis is an important animal pathogen that causes substantial economical loss in sheep and goat farming. Zoonotic infections in humans are rare, but when they occur they are often severe and difficult to treat. One of the most studied proteins from this bacterium, the secreted protein CP40 is being developed as a promising vaccine candidate and has been characterized as a serine protease. In this study we have investigated if CP40 is an endoglycosidase rather than a protease.ResultsCP40 does not show any protease activity and contains an EndoS-like family 18 of glycoside hydrolase (chitinase) motif. It hydrolyzes biantennary glycans on both human and ovine IgGs. CP40 is not a general chitinase and cannot hydrolyze bisecting GlcNAc.ConclusionTaken together we present solid evidence for re-annotating CP40 as an EndoS-like endoglycosidase. Redefining the activity of this enzyme will facilitate subsequent studies that could give further insight into immune evasion mechanisms underlying corynebacterial infections in animals and humans.
Highlights
C. pseudotuberculosis is an important animal pathogen that causes substantial economical loss in sheep and goat farming
CP40 is similar to EndoS-like enzymes CP40 has been described as a serine protease, but when we searched the protein databases, the protein did not show any significant sequence similarity with any known proteases except for nearly identical corynebacterial proteins that most likely are annotated based on the original characterization of CP40
We sequenced the cp40 gene in the DSM20689 used in this study, and this revealed that the coding sequence only differs in one nucleotide leading to one amino acid substation compared to cp40 in WA1030 used in the original characterization of the enzyme [27]
Summary
C. pseudotuberculosis is an important animal pathogen that causes substantial economical loss in sheep and goat farming. In this study we have investigated if CP40 is an endoglycosidase rather than a protease. Glycoproteins are essential for most biological pathways in eukaryotes and play important roles in the immune system of mammals [1, 2]. Alterations in glycosylation pattern on glycoproteins involved in the immune system are associated with disorders such as autoimmunity and cancer [3, 4]. There is a conserved N-linked glycosylation site on asparagine 297 in the CH2 domain of Fc of human IgG [5]. This N-297 glycosylation is essential for fine tuning
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