Construction of polypentagonal water networks on the A20I mutant. (A) Loop representation of the backbone structure of WT1 (PDB ID 5XQN) characterized with an internal-dyad motif with a local twofold axis of symmetry typical for Zoarcidae-derived IBPs. (B) Overlay of the backbone structures of WT1, WT2, A20L, A20T, A20V, A20I, and HPLC3 (PDB ID 1OPS). Two squares separated by a broken line indicate the location of two IBSs: one is the first prism plane (prism IBS, yellow) and another the pyramidal plane (pyramidal IBS, cyan). (C) Stereoview of the A20I structure with ∼50 semiclathrate waters constructing the polypentagonal network. A broken line indicates the boundary of the two IBSs. (D) A 60°-rotated image of the A20I structure showing the side of the polypentagonal networks that surround edge of the pyramidal IBS.