title: Giant DNA virus mimivirus encodes pathway for biosynthesis of unusual sugar 4-amino-4,6-dideoxy-D-glucose (Viosamine).
abstract: Mimivirus is one the largest DNA virus identified so far, infecting several Acanthamoeba species. Analysis of its genome revealed the presence of a nine-gene cluster containing genes potentially involved in glycan formation. All of these genes are co-expressed at late stages of infection, suggesting their role in the formation of the long fibers covering the viral surface. Among them, we identified the L136 gene as a pyridoxal phosphate-dependent sugar aminotransferase. This enzyme was shown to catalyze the formation of UDP-4-amino-4,6-dideoxy-D-glucose (UDP-viosamine) from UDP-4-keto-6-deoxy-D-glucose, a key compound involved also in the biosynthesis of L-rhamnose. This finding further supports the hypothesis that Mimivirus encodes a glycosylation system that is completely independent of the amoebal host. Viosamine, together with rhamnose, (N-acetyl)glucosamine, and glucose, was found as a major component of the viral glycans. Most of the sugars were associated with the fibers, confirming a capsular-like nature of the viral surface. Phylogenetic analysis clearly indicated that L136 was not a recent acquisition from bacteria through horizontal gene transfer, but it was acquired very early during evolution. Implications for the origin of the glycosylation machinery in giant DNA virus are also discussed.
authors.affiliation: Department of Experimental Medicine and Center of Excellence for Biomedical Research, University of Genova, Viale Benedetto XV/1, 16132 Genova, Italy.
authors.forename: Francesco
authors.initials: F
authors.lastname: Piacente
authors.forename: Margherita
authors.initials: M
authors.lastname: Marin
authors.forename: Antonio
authors.initials: A
authors.lastname: Molinaro
authors.forename: Cristina
authors.initials: C
authors.lastname: De Castro
authors.forename: Virginie
authors.initials: V
authors.lastname: Seltzer
authors.forename: Annalisa
authors.initials: A
authors.lastname: Salis
authors.forename: Gianluca
authors.initials: G
authors.lastname: Damonte
authors.forename: Cinzia
authors.initials: C
authors.lastname: Bernardi
authors.forename: Jean-Michel
authors.initials: JM
authors.lastname: Claverie
authors.forename: Chantal
authors.initials: C
authors.lastname: Abergel
authors.forename: Michela
authors.initials: M
authors.lastname: Tonetti
mesh_terms: D000048:Acanthamoeba / Q000821:virology; D004279:DNA, Viral / Q000235:genetics / Q000378:metabolism; D019143:Evolution, Molecular; D005814:Genes, Viral / Q000502:physiology; D005944:Glucosamine / Q000031:analogs & derivatives* / Q000235:genetics / Q000378:metabolism; D006031:Glycosylation; D056686:Mimiviridae / Q000201:enzymology* / Q000235:genetics*; D000637:Transaminases / Q000235:genetics* / Q000378:metabolism*; D014539:Uridine Diphosphate Sugars / Q000235:genetics / Q000378:metabolism
chemical_list: C492812:4-amino-4,6-dideoxyglucose; D004279:DNA, Viral; D014539:Uridine Diphosphate Sugars; D000637:Transaminases; D005944:Glucosamine