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Figure 4
The active site of MhGgH variants in complex with substrates. (a) Superposition of the active-site region of MhGgH D182A and E419A variants in complex with GG. The position of GG (dark or light orange for the D182A or E419A variants, respectively) in the active site of the D182A (light blue) and E419A (wheat) variants is stabilized mainly by direct hydrogen bonds or by water (w)-mediated contacts (dashed lines) with the labelled residues. Water molecules in the D182A and E419A variants are represented by red and salmon spheres, respectively. The catalytic residues (Asp182 and Glu419) are highlighted in red. (b) Superposition of the active-site region of the D182A–GG complex (light blue with the ligand in orange) with that of the MhGgH–Ser–GOL ternary complex (wheat). Hydrogen bonds between serine (cyan) or glycerol (yellow) and the residues of the active site are represented by dashed lines. (c) Superposition of the active-site regions of the MhGgH D182A and E419A variants in complex with MG. The hydrogen-bonding network stabilizing MG at the active site is similar to that observed for GG [interacting residues are shown as in (a)]. The newly established contacts are represented by dashed lines. Water molecules (w) are coloured as in (a). (d) Superposition of the active-site region of the E419A variant of MhGgH in complex with GG and MG and of the D182A variant in complex with MG (Glu419 in salmon). The hydrogen bonds between MhGgH and GG (orange) or MG (blue) are represented by black or grey dashed lines, respectively. The nucleophilic water (wn) is also indicated.

IUCrJ
Volume 6| Part 4| July 2019| Pages 572-585
ISSN: 2052-2525
https://doi.org/10.1107/S2052252519005372