FIG. 6.

Comparison of the extent of fusion promoted by wt F and L289A-F expressed with HN proteins carrying mutations for residues F220 and S222 at the membrane-proximal end of the dimer interface. Proteins are expressed in BHK cells 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 with wt HN and wt F. Error bars show the standard deviation from at least four independent determinations.