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Figure 6.
Figure 6. A stereo-illustration of the structural
conformations of key active-site residues of the N35D BCX
glycosyl-enzyme intermediate (N35D-2FXb) (dark gray)
superimposed upon those of the WT glycosyl-enzyme intermediate
(WT-2FXb) (light gray) (pH 7.5). Potential hydrogen bonds are
indicated by broken yellow lines, oxygen atoms are shown in red
and nitrogen atoms in blue. Modified Glu78-2FXb (Glu78*) is
covalently attached to a 2-fluoroxylobiosyl (2FXb) moeity where
the proximal saccharide is distorted to a ^2,5B conformation in
both N35D-2FXb and WT-2FXb. A crystallographically identifiable
water (Wat) molecule that is proposed to function in the
deglycosylation step of the reaction is indicated by a red
sphere. The most notable change is a reduction in the distance
between Asn35 N^δ2/Asp35 O^δ2 and Glu172 from 3.3 Å in
WT-2FXb to 2.7 Å in N35D-2FXb. See Table 3 for a listing
of additional interatomic distances.
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