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Figure 9
Superposition of high-resolution P21_a polymorph structure models. Superposition of the Cα atoms of residues 1–197 (the catalytic N-terminal domain) of 3CLpro. The figure illustrates the dramatic effect that intermolecular contacts can have on the plasticity of the C-terminal domain: while significant rearrangements of the C-terminal domain helices exist, as illustrated for the two most divergent models (red and blue), the helical region at the very end of the C-terminal fragment overlaps almost perfectly and maintains its orientation relative to the N-­terminal domain in all models. The final six residues diverge again and are either disordered or stabilized by intermolecular contacts. The red surface highlights the location of the binding site (ligand UAW246 in PDB entry 6xbg).

IUCrJ
Volume 8| Part 2| March 2021| Pages 238-256
ISSN: 2052-2525
https://doi.org/10.1107/S2052252521001159