A soluble form of the G glycoprotein, the attachment protein, of respiratory syncytial virus is shed from infected HEp-2 cells. The G(s) proteins of the Long and 18537 strains have apparent molecular sizes of 82 and 71 kilodaltons, respectively, 6 to 9 kilodaltons smaller than the virion-associated forms (G(v)). The G(s) protein of the Long strain was further characterized. Approximately one in six of all of the radiolabeled G molecules in these cultures at 24 h postinfection was present at the G(s) protein. The G(s) protein was clearly evident in culture fluids at 6 h postinfection, but the G(v) protein could not be discerned until 12 h after infection, and observation that is consistent with the 12-h eclipse period for respiratory syncytial virus. Therefore, The G(s) protein is shed, in part at least, from intact, infected cells and before the appearance of progeny virus. The appearance of a smaller G(s) protein (74 kilodaltons) in fluids of infected calls which were incubated with tunicamycin shows that addition of N-linked oligosaccharides is not required for the genesis and shedding of the G(s) protein. Sequencing of the amino terminus of purified G(s) protein revealed two different termini, whose generations are consistent with cleavages of the full-length G protein between amino acids 65 and 66 and between 74 and 75. This result suggests that the G5 protein is present in two different forms which lack the proposed intracytoplasmic and transmembrane domains of the full-length G protein.
ASJC Scopus subject areas
- Insect Science