FIG 4.

Effects of the 205-72 pair on HA sensitivity to acidic pH in HA-mediated cell-cell fusion. The fusion indexes of each HA containing different residues in 205-72 pair-mediated cell-cell fusion are compared. To obtain the fusion index, the fusions in each fusion curve (response to pH) were normalized to the maximum fusion for that curve. (A) Comparison of wild-type Bris H-K, R-K, and E-K HA sensitivity to pH. (B) Comparison of wild-type Bris H-K, A-K, Q-K, Y-K, D-K, and F-K HA sensitivity to pH. Fusion data are shown as the means from three independent experiments.