Fusion induced by class II and III fusion proteins is voltage dependent.

<p>Extents of cell-cell fusion induced by fusion proteins from the three viral classes. The fusion proteins were: class I–Influenza HA (Flu), ASLV Env, JRSV Env, and HIV Env; class II–SFV E1/E2, RRV E1/E2, Sindbis E1/E2, VEEV E; class III–VSV G and a mutant (gB801) of EBV (class III). Fusion was independent of voltage for the four class I proteins tested. In contrast, fusion was significantly greater at negative (filled bars) than positive potentials (open bars) for all class II and III proteins. Effector cells were transfected with the proteins of the indicated viral types. Voltage was made positive by adding the Na⁺ ionophore SQI-Pr (30 µM). Error bars are SEM (n = 3).