The rare sugarN-acetylated viosamine is a major component of Mimivirus fibers.
The giant virus Mimivirus encodes an autonomous glycosylation system that is thought to be responsible for the formation of complex and unusual glycans composing the fibers surrounding its icosahedral capsid, including the dideoxyhexose viosamine. Previous studies have identified a gene cluster in the virus genome, encoding enzymes involved in nucleotide-sugar production and glycan formation, but the functional characterization of these enzymes and the full identification of the glycans found in viral fibers remain incomplete. Because viosamine is typically found in acylated forms, we suspected that one of the genes might encode an acyltransferase, providing directions to our functional annotations. Bioinformatic analyses indicated that the L142 protein contains an N-terminal acyltransferase domain and a predicted C-terminal glycosyltransferase. Sequence analysis of the structural model of the L142 N-terminal domain indicated significant homology with some characterized sugar acetyltransferases that modify the C-4 amino group in the bacillosamine or perosamine biosynthetic pathways. Using mass spectrometry and NMR analyses, we confirmed that the L142 N-terminal domain is a sugar acetyltransferase, catalyzing the transfer of an acetyl moiety from acetyl-CoA to the C-4 amino group of UDP-d-viosamine. The presence of acetylated viosaminein vivohas also been confirmed on the glycosylated viral fibers, using GC-MS and NMR. This study represents the first report of a virally encoded sugar acetyltransferase.
From the Department of Experimental Medicine and Center of Excellence for Biomedical Research, University of Genova, 16126 Genova, Italy.
Francesco
F
Piacente
the Departments of Agricultural Sciences and.
Cristina
C
De Castro
the Aix-Marseille Université, Centre National de la Recherche Scientifique, Information Génomique et Structurale, UMR 7256, IMM FR3479, 13288 Marseille Cedex 9, France.
Sandra
S
Jeudy
From the Department of Experimental Medicine and Center of Excellence for Biomedical Research, University of Genova, 16126 Genova, Italy.
Matteo
M
Gaglianone
From the Department of Experimental Medicine and Center of Excellence for Biomedical Research, University of Genova, 16126 Genova, Italy.
Maria Elena
ME
Laugieri
the Aix-Marseille Université, Centre National de la Recherche Scientifique, Information Génomique et Structurale, UMR 7256, IMM FR3479, 13288 Marseille Cedex 9, France.|Chemical Sciences, University of Napoli, 80138 Napoli, Italy, and.
Anna
A
Notaro
From the Department of Experimental Medicine and Center of Excellence for Biomedical Research, University of Genova, 16126 Genova, Italy.
Annalisa
A
Salis
From the Department of Experimental Medicine and Center of Excellence for Biomedical Research, University of Genova, 16126 Genova, Italy.
Gianluca
G
Damonte
the Aix-Marseille Université, Centre National de la Recherche Scientifique, Information Génomique et Structurale, UMR 7256, IMM FR3479, 13288 Marseille Cedex 9, France.
Chantal
C
Abergel
From the Department of Experimental Medicine and Center of Excellence for Biomedical Research, University of Genova, 16126 Genova, Italy, tonetti@unige.it.
Michela G
MG
Tonetti
D000217:Acyltransferases / Q000737:chemistry* / Q000378:metabolism; D036022:Capsid Proteins / Q000737:chemistry* / Q000378:metabolism; D006031:Glycosylation; D056686:Mimiviridae / Q000201:enzymology*; D000072417:Protein Domains
D036022:Capsid Proteins; D000217:Acyltransferases
Mimivirus; acetyl coenzyme A (acetyl-CoA); glycosylation; mass spectrometry (MS); nuclear magnetic resonance (NMR); viosamine; virus