Structure of the stable sNS1 tetramer. a Two NS1 dimeric structures fitted into the cryoEM map (reduced sharpening was applied to make the density of the elongated β-sheet clearer). One dimer is colored in pink and light green and the other in yellow and light blue. b Left: the overall structure of the sNS1 dimer is similar to that of iNS1 except for the β-roll region (residues 1–30) in iNS1, which is an elongated β-sheet (residues 18–27) in sNS1. View from the elongated β-sheet of the black boxed region in a. The respective elongated β-strand of each protomer is highlighted in a darker shade of the same color (red and dark green). Right: surface density map with the regions corresponding to the elongated β-sheet colored in green, and the rest of the map in yellow. c Interaction of the elongated β-strands between the two dimers (red/green and yellow/blue). (i) Top view showing the elongated β-sheets of the red/green dimer interacting with that of the yellow/blue dimer (only its elongated β-sheet is shown). (ii) Side view showing possible hydrogen bonds or electrostatic interactions between the two elongated β-sheets from opposite dimers (dotted black lines). These interactions are identified by the distance between Cα backbone (
