TABLE 3.

Fusion promotion ability of active site NDV HN mutants^a

Mutant or other classification	Fusionc
Wild type	100
R174A	—b
R174K	6 ± 0.6
R416A	35 ± 2.5
R416D	89 ± 4.3
R416E	97 ± 5.2
R416K	35 ± 3.5
R498A	92 ± 4.1
R498Q	81 ± 2.8
I175E	151 ± 11.6
I175L	102 ± 9.3
I175T	86 ± 5.1
E258D	82 ± 3.1
E258S	79 ± 5.2
Y299A	78 ± 1.2
Y317F	83 ± 3.7
E401D	107 ± 6.2
E547D	13 ± 3.9
Y526F	129 ± 9.3
Y526H	149 ± 15.4

^aCell fusion was calculated from the ratio of the total number of nuclei found in syncytia to the total number of nuclei counted in three or four randomly chosen fields under a light microscope. The values indicated represent the average percentage found in three independent experiments of fusion to wild-type NDV HN when it is coexpressed with the gene encoding NDV F protein in HeLa cells.

^b—, no syncytia observed.