The active site of GalrD-II. Panel A, Se-Met GalrD-II in the presence of Mg2+ (PDB Code 2OQY). Panel B, Wild type (S-Met) GalrD-II in the presence of Mg2+ and L-malate (PDB Code 3ES7). Panel C, Y90F mutant of GalrD-II in the presence of Mg2+ and galactarate (PDB Code 3HPF). The Mg2+ ions are highlighted in green, L-malate is highlighted in cyan (panel B), and galactarate is highlighted in yellow (panel C). The active site residues are labelled only in panel B for clarity.