Acanthamoeba polyphaga mimivirus is a giant virus encoding 1'262 genes among which many were previously thought to be exclusive to cellular life. For example, mimivirus genes encode enzymes involved in the biosynthesis of nucleotide sugars and putative glycosyltransferases. We identified in mimivirus a glycogenin-1 homologous gene encoded by the open reading frame R707. The R707 protein was found to be active as a polymerizing glucosyltransferase enzyme. Like glycogenin-1 R707 activity was divalent metal ion dependent and relied on an intact DXD motif. In contrast to glycogenin-1, R707 was however not self-glucosylating. Interestingly, the product of R707 catalysis featured α1-6, β1-6, and α1-4 glycosidic linkages. Mimivirus R707 is the first reported glycosyltransferase able to catalyze the formation of both α and β linkages. Mimivirus encoded glycans play a role in the infection of host amoeba. Co-infection of Acanthamoeba with mimivirus and amylose and chitin hydrolysate reduced the number of infected amoeba, thus supporting the importance of polysaccharide chains in the uptake of mimivirus by amoeba. The identification of a glycosyltransferase capable of forming α and β linkages underlines the peculiarity of mimivirus and enforces the concept of a host-independent glycosylation machinery in mimivirus.
- giant virus
- NMR spectroscopy
- ©2016 The Author(s)
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