Fig 6.

Engagement of site II of the receptor binding protein is required for activation of NiV F. 293T cells coexpressing NiV F with the NiV-NDV chimeric binding protein were allowed to bind to receptor-bearing RBCs at 4°C in the absence (A) or presence (B) of zanamivir. Zanamivir was added to activate NDV HN site II. Unbound RBCs were then washed, and standard medium without (A) or with (B) zanamivir, for the activation of binding site II, was added at 37°C for 120 min. The 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 A and that there are no released cells (□) in panel B. The values are means (± the standard errors) of results from three experiments.