Abstract
Cell attachment and membrane penetration are functions of the rotavirus outer capsid spike protein, VP4. An activating tryptic cleavage of VP4 produces the N-terminal fragment, VP8*, which is the viral hemagglutinin and an important target of neutralizing antibodies. We have determined, by X-ray crystallography, the atomic structure of the VP8* core bound to sialic acid and, by NMR spectroscopy, the structure of the unliganded VP8* core. The domain has the beta-sandwich fold of the galectins, a family of sugar binding proteins. The surface corresponding to the galectin carbohydrate binding site is blocked, and rotavirus VP8* instead binds sialic acid in a shallow groove between its two beta-sheets. There appears to be a small induced fit on binding. The residues that contact sialic acid are conserved in sialic acid-dependent rotavirus strains. Neutralization escape mutations are widely distributed over the VP8* surface and cluster in four epitopes. From the fit of the VP8* core into the virion spikes, we propose that VP4 arose from the insertion of a host carbohydrate binding domain into a viral membrane interaction protein.
Publication types
- Comparative Study
- Research Support, Non-U.S. Gov't
- Research Support, U.S. Gov't, Non-P.H.S.
- Research Support, U.S. Gov't, P.H.S.
MeSH terms
- Amino Acid Sequence
- Binding Sites
- Capsid / chemistry*
- Capsid / physiology
- Capsid Proteins*
- Carbohydrate Metabolism*
- Consensus Sequence
- Crystallography, X-Ray
- Epitopes / chemistry
- Evolution, Molecular
- Galectins
- Hemagglutinins / chemistry
- Hemagglutinins, Viral / biosynthesis
- Hemagglutinins, Viral / chemistry
- Hydrogen Bonding
- Models, Molecular
- Molecular Sequence Data
- N-Acetylneuraminic Acid / metabolism*
- Nuclear Magnetic Resonance, Biomolecular
- Peptide Fragments / chemistry
- Protein Binding
- Protein Conformation
- Protein Folding
- Protein Structure, Secondary
- Protein Structure, Tertiary
- RNA-Binding Proteins / biosynthesis
- RNA-Binding Proteins / chemistry
- Recombinant Fusion Proteins / chemistry
- Rotavirus / chemistry*
- Rotavirus / physiology
- Structure-Activity Relationship
- Substrate Specificity
- Viral Nonstructural Proteins / biosynthesis
- Viral Nonstructural Proteins / chemistry
- Virion / chemistry
- Virion / ultrastructure
Substances
- Capsid Proteins
- Epitopes
- Galectins
- Hemagglutinins
- Hemagglutinins, Viral
- Peptide Fragments
- RNA-Binding Proteins
- Recombinant Fusion Proteins
- VP4 protein, Rotavirus
- Viral Nonstructural Proteins
- nsp1 protein, Rotavirus
- NS35 protein, rotavirus
- N-Acetylneuraminic Acid