title: The rhesus rotavirus VP4 sialic acid binding domain has a galectin fold with a novel carbohydrate binding site.
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.
authors.affiliation: Laboratory of Molecular Medicine, Enders 673, Children's Hospital, 320 Longwood Avenue, Boston, MA 02115, USA. dormitze@crystal.harvard.edu
authors.forename: Philip R
authors.initials: PR
authors.lastname: Dormitzer
authors.forename: Zhen-Yu J
authors.initials: ZY
authors.lastname: Sun
authors.forename: Gerhard
authors.initials: G
authors.lastname: Wagner
authors.forename: Stephen C
authors.initials: SC
authors.lastname: Harrison
mesh_terms: D000595:Amino Acid Sequence; D001665:Binding Sites; D002213:Capsid / Q000737:chemistry* / Q000502:physiology; D036022:Capsid Proteins; D050260:Carbohydrate Metabolism; D016384:Consensus Sequence; D018360:Crystallography, X-Ray; D000939:Epitopes / Q000737:chemistry; D019143:Evolution, Molecular; D037161:Galectins; D006388:Hemagglutinins / Q000737:chemistry; D006389:Hemagglutinins, Viral / Q000096:biosynthesis / Q000737:chemistry; D006860:Hydrogen Bonding; D008958:Models, Molecular; D008969:Molecular Sequence Data; D019158:N-Acetylneuraminic Acid / Q000378:metabolism*; D019906:Nuclear Magnetic Resonance, Biomolecular; D010446:Peptide Fragments / Q000737:chemistry; D011485:Protein Binding; D011487:Protein Conformation; D017510:Protein Folding; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D016601:RNA-Binding Proteins / Q000096:biosynthesis / Q000737:chemistry; D011993:Recombinant Fusion Proteins / Q000737:chemistry; D012401:Rotavirus / Q000737:chemistry* / Q000502:physiology; D013329:Structure-Activity Relationship; D013379:Substrate Specificity; D017361:Viral Nonstructural Proteins / Q000096:biosynthesis / Q000737:chemistry; D014771:Virion / Q000737:chemistry / Q000648:ultrastructure
chemical_list: D036022:Capsid Proteins; D000939:Epitopes; D037161:Galectins; D006388:Hemagglutinins; D006389:Hemagglutinins, Viral; D010446:Peptide Fragments; D016601:RNA-Binding Proteins; D011993:Recombinant Fusion Proteins; C060339:VP4 protein, Rotavirus; D017361:Viral Nonstructural Proteins; C104282:nsp1 protein, Rotavirus; C079234:NS35 protein, rotavirus; D019158:N-Acetylneuraminic Acid