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Figure 3.
Figure 3. Stereo images of models of substrate with mutase.
(a) The initial complex between UDP-galactose of the active
reduced form of the K. pneumoniae enzyme. This complex is
predicted to occur in a mechanism involving electron transfer or
a covalent intermediate. No significant re-arrangements are
required to accommodate the substrate. The structurally diverse
loop 5 is shown in pink. (b) A model of the covalent adduct with
the re-face buckle of isoalloxazine ring. The re-face buckled
isoalloxazine ring is taken from a thioredoxin structure.17 This
model allows interactions with key conserved residues. The model
would require conformation changes in side-chain positions only
to avoid steric clashes. (c) The covalent adduct based on the
experimental K. pneumoniae FADH - structure. The sugar is
interpenetrating with the protein structure. Either FADH -
adopts a different buckle in the presence of substrate or the
protein undergoes a profound conformation change. His63 has been
omitted for clarity and Pro59 has been added to this Figure.
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