Identification of an outer capsid glycoprotein of human rotavirus by concanavalin A

An outer capsid glycoprotein of human rotavirus (serotype 1) was localized and characterized by use of lectins, electron microscopy and a modified Western blotting technique. Lectins with specificity for fucose, galactose, glucose and mannose were mixed with purified single- or double-shelled human rotavirus. Aggregates observed by electron microscopy were obtained with double-shelled virus and concanavalin A, the only tested lectin with mannose specificity. By SDS-polyacrylamide gel electrophoretic analysis nine structural polypeptides could be identified. Five of these polypeptides were components of the inner capsid (VP1, VP2, VP3, VP4, VP6) and four components of the outer capsid (VP5, VP7, VP8, VP9). When using a modified Western blotting technique employed for glycoprotein detection, only VP7 was found to be glycosylated. This glycoprotein could be identified in rotavirus from human stools as well as from cell cultures. Heterogeneity in molecular weight of VP7 was observed in different isolates. An unexpected heterogeneity of VP7 was seen within a human rotavirus strain. An unplaqued stock of virus was found to exhibit two distinguishable glycoprotein bands (VP7, VP7a). After 10 passages in MA-104 cells the same strain was found to exhibit only one glycoprotein band.