Fig. 2.
Structure of HE and comparison to HEF. (A) Ribbon representation of the BCoV HE dimer. One HE monomer is colored gray, the other by domain: lectin domain (R, blue) with bound αNeu4,5,9Ac32Me (cyan sticks) and potassium ion (magenta sphere); esterase domain (E, green) with Ser-His-Asp active site triad (magenta sticks); membrane-proximal domain (MP, red). (B) Structure of the influenza C HEF trimer. One monomer is colored by domain with domains R and E color-coded as in a; the fusion domain F is shown in red. Remaining monomers are shown in pink or gray. (C) Linear order of the sequence segments in HE and HEF color-coded by domains as in a and b. Gray segments indicate the transmembrane domain in HE and the fusion peptide in HEF. The arrowhead indicates the HEF cleavage site. (D) Top views showing the arrangement of the lectin domains in the BCoV HE homodimer (Left) and the influenza C HEF homotrimer (Right). The four-stranded β-sheets forming a continuous eight-stranded β-sheet in the HE dimer are emphasized by darker coloring.