FIG 3.

All subunits from the wY132A crystal structure asymmetric unit adopt one conformation. Structure alignment of the AB dimer and CD dimer (PDB accession code 6ECS) shows that the two dimers have similar tertiary structures (shown in side view in panel a and top view in panel b). Overlapping all subunits (A, B, C, and D) shows that all subunits from the asymmetric unit exhibit a single conformation (shown in side view in panel c and top view in panel d). (e) To quantitively compare four subunits, the Cα displacements of chain B, C, and D relative to chain A were calculated and plotted against residue number. Most of the residues have displacements of less than 1 Å, indicating that all four subunits have a similar tertiary structures. The exceptions to this generalization are the spike tips and the C terminal regions, including where electron density starts to degrade.