FIG. 3.
Analysis of GP64-mediated membrane fusion. (A) Summary of results from syncytium formation assays of cells infected with viruses expressing wild-type GP64 (AcMNPV and vAcGP64wt) or viruses expressing palmitoylation-minus GP64 proteins (vAcGP64C503A and vAcGP64C503S). Sf9 cells were infected with the indicated viruses at an MOI of 10. At 36 h p.i., cells were incubated in PBS buffer that was adjusted to the indicated pH value (from pH 5.0 to 6.0) for 20 min. Cells were scored as positive for syncytium formation when at least five nuclei were detected in a syncytial mass (+++, >20 syncytia per well; ++, 11 to 20 syncytia per well; +, 1 to 10 syncytia per well; −, no syncytia observed). (B) Examples of syncytium formation in Sf9 cells expressing wild-type GP64 and exposed to PBS at pH 5.0 or 6.0. Syncytial masses are indicated by open arrowheads.