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Figure 7
The active site of EcAII in complex with L-Asp from the PDB entry 3eca, chain A (Swain et al., 1993View full citation). The two potential nucleophilic Thr residues, Thr12 and Thr89, are in ball-and-stick representation. Thr89 is part of the Thr89–Lys162–Asp90 T-K-D triad (labeled). The oxyanion hole is marked by blue ovals. Water molecules are shown as small red spheres. The most important hydrogen bonds are marked by black dashed lines. Note that in this type II enzyme, the hydrogen-bonded Thr12⋯Tyr25 residues come from the same subunit. In type I asparaginases the Tyr residue of this pair is contributed by the complementary subunit from the intimate dimer of the tetrameric assembly.

IUCrJ
Volume 13| Part 2| March 2026| Pages 132-145
ISSN: 2052-2525
https://doi.org/10.1107/S2052252525010826