FIG 3.

Mutations in gH substitute for gL function in transient-transfection fusion assays. To test whether the mutations present in gH^B4.1 are sufficient to compensate for lack of gL, RK13 cells were cotransfected with expression plasmids for gB^Ka and gH^Ka or gH^B4.1 in the presence or absence of gL expression as indicated. Results from assays with gB^Ka, gH^Ka, and gL were set as 100%. As a negative control, an assay with the gB^Ka expression plasmid only (the DNA amount was adjusted by addition of empty vector) was used. The relative fusion activity (number of syncytia × syncytium area) with corresponding standard deviation from three independent experiments is depicted.