FIG. 2.

The promotion of fusion by L289A-F expressed alone and with wt HN in different cell lines. The mutated F protein is expressed both with and without HN in BHK, HeLa-T4, Hep-2, and CV-1 cells from the pBSK vector driven by the vaccinia virus-T7 RNA polymerase expression system. The extent of fusion is quantitated with the content-mixing fusion assay and expressed as the percentage of that obtained in the same cell line with HN and wt F. Error bars show the standard deviation from at least four independent determinations.