title: Giant mimivirus R707 encodes a glycogenin paralogue polymerizing glucose through α- and β-glycosidic linkages.
abstract: Acanthamoeba polyphaga mimivirus is a giant virus encoding 1262 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 with 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 catalyse the formation of both α and β linkages. Mimivirus-encoded glycans play a role in the infection of host amoebae. Co-infection of Acanthamoeba with mimivirus and amylose and chitin hydrolysate reduced the number of infected amoebae, thus supporting the importance of polysaccharide chains in the uptake of mimivirus by amoebae. 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.
authors.affiliation: Institute of Physiology, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland.
authors.forename: Anna J
authors.initials: AJ
authors.lastname: Rommel
authors.affiliation: Institute of Physiology, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland.
authors.forename: Andreas J
authors.initials: AJ
authors.lastname: Hülsmeier
authors.affiliation: Institute of Organic Chemistry, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland.
authors.forename: Simon
authors.initials: S
authors.lastname: Jurt
authors.affiliation: Institute of Physiology, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland.
authors.forename: Thierry
authors.initials: T
authors.lastname: Hennet
mesh_terms: D000048:Acanthamoeba / Q000821:virology*; D005947:Glucose / Q000737:chemistry / Q000378:metabolism*; D005964:Glucosyltransferases / Q000737:chemistry / Q000378:metabolism*; D006023:Glycoproteins / Q000737:chemistry / Q000378:metabolism*; D006027:Glycosides / Q000737:chemistry / Q000378:metabolism; D006031:Glycosylation; D016695:Glycosyltransferases / Q000378:metabolism; D056686:Mimiviridae / Q000378:metabolism* / Q000472:pathogenicity*; D014764:Viral Proteins / Q000737:chemistry / Q000378:metabolism*
chemical_list: D006023:Glycoproteins; D006027:Glycosides; D014764:Viral Proteins; C051887:glycogenin; D016695:Glycosyltransferases; D005964:Glucosyltransferases; D005947:Glucose
keywords: NMR spectroscopy; giant virus; glycogen; glycosylation; polysaccharide