FIG. 3.

Structure of the fusion loop region of the sE trimer. Closeup of the aromatic anchor formed by Trp-101 and Phe-108 in the fusion loops (orange) of DEN-1 sE (A) and DEN-2 sE (B). The chloride ion (black) is shifted by 1.9 Å along the threefold axis in DEN-1 sE relative to its position in DEN-2 sE. The three clustered fusion loops form an apex that is mesa shaped in DEN-1 sE (C and E) and bowl shaped in DEN-2 sE (D and F). The view in panels E and F is down the threefold axis and rotated 90° relative to the views of the other panels.