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Figure 2.
Fig. 2. Structure of the ligands and the active site of
Glu1E191D. (A) The natural substrate DIMBOAGlc (Left), the
aglycone DIMBOA (Center), and the competitive inhibitor dhurrin
(Right). (B) Ribbon diagram of the structure of the maize  -glucosidase
Glu1 and its inactive Glu1E191D mutant, showing the catalytic
residues E191 (D191 in the mutant) and E406 (red), four residues
(F198, F205, W378, and F466) forming the aglycone-binding pocket
(blue), and two other residues (A467 and Y473) that are probably
important for aglycone recognition (yellow). Different colors
and the color transitions in  -helices
and -strands
trace the polypeptide backbone in the barrel-shaped
three-dimensional structure from the N terminus (dark blue) to
the C terminus (dark red) direction. The figure was produced
with MOLSCRIPT (35) and RASTER3D (36). (C) Electrostatic surface
representation of the active site region of Glu1E191D showing
positively charged regions in blue, negatively charged regions
in red, and neutral regions in white. The slot-like active site,
measuring 23 Å × 7.1 Å at the entrance,
contains the natural substrate DIMBOAGlc in compact
representation with standard atom-type colors. In this view,
only the aglycone moiety is visible in its binding site as
glucose is hidden below aglycone. C was produced with GRASP (37).
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