Novel fold of rotavirus glycan-binding domain predicted by AlphaFold2 and determined by X-ray crystallography

Group B rotaviruses have a unique fold in the glycan-binding domain specific for N- acetyllactosamine that potentially diverged from folds conserved in group A and C rotaviruses. The VP8* domain of spike protein VP4 in group A and C rotaviruses, which cause epidemic gastroenteritis in children, exhibits a conserved galectin-like fold for recognizing glycans during cell entry. In group B rotavirus, which causes significant diarrheal outbreaks in adults, the VP8* domain (VP8*B) surprisingly lacks sequence similarity with VP8* of group A or group C rotavirus. Here, by using the recently developed AlphaFold2 for ab initio structure prediction and validating the predicted model by determining a 1.3-angstrom crystal structure, we show that VP8*B exhibits a novel fold distinct from the galectin fold. This fold with a beta-sheet clasping an alpha-helix represents a new fold for glycan recognition based on glycan array screening, which shows that VP8*B recognizes glycans containing N-acetyllactosamine moiety. Although uncommon, our study illustrates how evolution can incorporate structurally distinct folds with similar functionality in a homologous protein within the same virus genus.

Automated summary

The VP8*B structure of group B rotavirus displays a novel fold for glycan recognition distinct from the galectin fold seen in group A and C rotaviruses. This study demonstrates how evolution can incorporate structurally distinct folds with similar functionality within the same virus genus.