Fig. 5: Predictions of catalytic water molecules and water molecule network densities in HvExoI computational models of wild-type (WT) and E220A covalent complexes.

a Prevalence of catalytic water molecules (cpk spheres) in computational models of WT and E220A are shown for three selected frames (represented by N219, E220/E220A, D285-Glc adduct) along cMD simulations. Separations of water molecules (cpk spheres) from Oε1 and Oε2 atoms of E491 at ≤2.9 Å are indicated in dashed lines. Properties of surface morphologies coloured by electrostatic potentials are described in Fig. 1. Selected Glc moieties of L5 are displayed. b Predicted water molecule network densities in superposed (RMSD value 0.13 Å) WT (PDB 3WLH) and E220A (PDB 8HJ7) structures in-complex with Glc using WaterKit²⁹. Images of WT (blue surface contoured at −1 kT e⁻¹ level) and E220A (orange mesh contoured at −1 kT e⁻¹ level) depict clusters of water molecules (red and blue spheres for WT and E220A, respectively). Alternate water molecule dispositions in E220A are marked in an ellipsoid. Key active site residues and Glc molecules (cpk sticks) are indicated for WT (cyan cpk sticks) and E220A (orange cpk sticks). Properties of a surface morphology of WT coloured by an electrostatic potential are described in Fig. 1. c Retaining catalytic mechanism of HvExoI and averages of catalytic water molecules (%) of all water molecules identified in replicates 1–3 in WT and E220A covalent complexes. d Snapshots from molecular animations illustrating the participation of catalytic water molecules (red spheres) in active site residues of WT and E220A covalent complexes, predicted by DynaWatProt³⁰. Protein folds are shown in lime green (WT) and light blue (E220A) and correspondingly coloured residues in cpk sticks, with L5 substrate surfaces indicated in a mesh. Subsites −1 and +1 are marked in all images.