Oligosaccharide composition of calf rotavirus

Area of Science:

• Virology
• Glycobiology
• Structural Biology

Background:

• Rotavirus VP7 is a key structural glycoprotein involved in viral assembly and immunity.
• Understanding the glycosylation of VP7 is crucial for elucidating its role in viral pathogenesis and for vaccine development.

Purpose of the Study:

• To characterize the oligosaccharide structures attached to the VP7 glycoprotein of calf rotavirus.
• To determine the number and type of N-linked oligosaccharides present on VP7.

Main Methods:

• Analysis of tunicamycin-treated infected cells to identify VP7 precursor.
• Endoglycosidase H digestion of mature rotavirus VP7.
• Size exclusion chromatography (Bio-Gel P-4 and P-2) of digested oligosaccharides.
• Enzymatic digestion with mannosidase to further analyze oligosaccharide composition.

Main Results:

• VP7 precursor lacking glycosylation showed a molecular weight reduction of approximately 6000 Da.
• Endo H digestion yielded a molecular weight decrease of approximately 5000 Da in two stages.
• The predominant oligosaccharide released had a molecular weight of 1350 Da.
• Further digestion revealed the oligosaccharide comprised seven mannose residues (Man)7, with a 6:1 ratio of mannose to a smaller oligosaccharide fragment, indicating four N-linked oligosaccharides.

Conclusions:

• The oligosaccharides of calf rotavirus VP7 are N-linked and composed of (Man)7 residues.
• Two oligosaccharides are accessible (exposed) and two are less accessible (cryptic) within the VP7 structure.
• These findings contribute to understanding rotavirus glycoprotein structure and potential targets for antiviral strategies.