N-Linked Glycans of Chloroviruses Sharing a Core Architecture without Precedent

N-glycosylation is afundamental modification of proteins and exists in the three domains of life and in some viruses,including the chloroviruses,for whichanew type of core N-glycan is herein described. This N-glycan core struc- ture,common to all chloroviruses,isapentasaccharide with a b-glucose linked to an asparagine residue which is not located in the typical sequon N-X-T/S.The glucose is linked to aterminal xylose unit and ahyperbranched fucose,which is in turn substituted with aterminal galactose and asecond xylose residue.The thirdposition of the fucose unit is always linked to arhamnose,which is asemiconserved element because its absolute configuration is virus-dependent. Additional decora- tions occur on this core N-glycan and represent amolecular signature for each chlorovirus.