Fig 9.

Amino acids 181 and 182 regulate an early stage in F activation. 293T cells expressing the NiV-NDV chimeric binding protein alone (B) or coexpressing with NiV F (A) were allowed to bind to receptor-bearing RBCs at 4°C in the presence of zanamivir. Unbound RBCs were then removed, and medium with zanamivir, to activate binding site II, was added, followed by incubation at 37°C for 90 min. After incubation, the cells were washed, and medium at pH 6.5 was added. The cells were incubated at 37°C for 75 min. Values on the y axis reflect quantification of RBCs that were (i) released (□), (ii) bound (▩), or (iii) fused (■). Note that there is no fusion (■) in panel B, and there are no bound cells (▩) in panel A. The values are means (± the standard errors) of results from three experiments.