Expanding the Occurrence of Polysaccharides to the Viral World: The Case of Mimivirus

• Published in: Angewandte Chemie Vol. 133; no. 36; pp. 20050 - 20057
• Main Authors: Notaro, Anna, Couté, Yohann, Belmudes, Lucid, Laugeri, Maria Elena, Salis, Annalisa, Damonte, Gianluca, Molinaro, Antonio, Tonetti, Michela G., Abergel, Chantal, De Castro, Cristina
• Format: Journal Article
• Language: English
• Published: Weinheim Wiley Subscription Services, Inc 01.09.2021
• Subjects: Blurring; Capsids; Chemistry; Genomes; giant viruses; glycans; glycocalyx; Glycosylation; Machinery; Macromolecules; Mimivirus; NMR spectroscopy; Oligosaccharides; Polysaccharides; Saccharides; Viruses
• ISSN: 0044-8249; 1521-3757
• DOI: 10.1002/ange.202106671

The general perception of viruses is that they are small in terms of size and genome, and that they hijack the host machinery to glycosylate their capsid. Giant viruses subvert all these concepts: their particles are not small, and their genome is more complex than that of some bacteria. Regarding glycosylation, this concept has been already challenged by the finding that Chloroviruses have an autonomous glycosylation machinery that produces oligosaccharides similar in size to those of small viruses (6–12 units), albeit different in structure compared to the viral counterparts. We report herein that Mimivirus possesses a glycocalyx made of two different polysaccharides, now challenging the concept that all viruses coat their capsids with oligosaccharides of discrete size. This discovery contradicts the paradigm that such macromolecules are absent in viruses, blurring the boundaries between giant viruses and the cellular world and opening new avenues in the field of viral glycobiology. The giant virus Mimivirus has an icosahedral capsid embedded in a thick layer of fibrils, resembling the glycocalyx of many bacteria. This study revealed that these fibrils are composed by a limited set of carrier proteins which bear two distinct polysaccharides. The presence of polysaccharides refutes the paradigm that such macromolecules are absent in viruses and opens new avenues in the field of glycosciences and viral biology.