The soluble form of human respiratory syncytial virus attachment protein differs from the membrane-bound form in its oligomeric state but is still capable of binding to cell surface proteoglycans.
The soluble (Gs) and membrane-bound (Gm) forms of human respiratory syncytial virus (HRSV) attachment protein were purified by immunoaffinity chromatography from cultures of HEp-2 cells infected with vaccinia virus recombinants expressing either protein. Sucrose gradient centrifugation indicated that Gs, which is secreted into the culture medium, remains monomeric, whereas Gm is an oligomer, probably a homotetramer. Nevertheless, Gs was capable of binding to the surface of cells in vitro, as assessed by a flow cytometry-based binding assay. The attachment of Gs to cells was inhibited by previous heparinase treatment of living cells, and Gs did not bind to CHO cell mutants defective in proteoglycan biosynthesis. Thus, Gs, as previously reported for the G protein of intact virions, binds to glycosaminoglycans presented at the cell surface as proteoglycans. Deletion of a previously reported heparin binding domain from Gs protein substantially inhibited its ability to bind to cells, but the remaining level of binding was still sensitive to heparinase treatment, suggesting that other regions of the Gs molecule may contribute to attachment to proteoglycans. The significance of these results for HRSV infection is discussed.
Escribano-Romero
Estela
E
Biología Viral, Centro Nacional de Microbiología, Instituto de Salud Carlos III, Majadahonda, 28220 Madrid, Spain.
Rawling
Joanna
J
García-Barreno
Blanca
B
Melero
José A
JA
D000595:Amino Acid Sequence; D000818:Animals; D016466:CHO Cells; D045744:Cell Line, Tumor; D002462:Cell Membrane / Q000378:metabolism*; D002499:Centrifugation, Density Gradient; D006224:Cricetinae; D006025:Glycosaminoglycans / Q000378:metabolism; D006493:Heparin / Q000378:metabolism; D019763:Heparin Lyase / Q000378:metabolism; D006801:Humans; D008969:Molecular Sequence Data; D011485:Protein Binding; D020836:Protein Structure, Quaternary; D017434:Protein Structure, Tertiary; D011509:Proteoglycans / Q000378:metabolism*; D018113:Respiratory Syncytial Virus, Human / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D012995:Solubility; D014764:Viral Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*
D006025:Glycosaminoglycans; D011509:Proteoglycans; D014764:Viral Proteins; D006493:Heparin; D019763:Heparin Lyase