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Figure 2.
Figure 2. (a) Stereo view of the E186Q/maltopentaose (shown
in magenta) superimposed on the wild-type/maltose (shown in
yellow) structure at the active site. The protein residues of
each complex were superimposed using the RIGID program of
TURBO-FRODO. Comparison of the two structures revealed almost
the same conformation at the active site, except for in the
main-chain region around the Thr342 residue. (b) Comparison of
the hydrogen bonding pattern between the structures of
E186Q/maltopentaose (magenta) and wild-type/maltose (yellow)
around subsites -1 and +1 in stereo. The dotted lines indicate
the hydrogen bond interactions. A putative attacking water
molecule (H[2]O 712) was observed at the position corresponding
to the O1 atom of Glc( -1) in the wild-type/maltose structure.
The intramolecular hydrogen bonds between Glu186, Arg188, and
Tyr192 were not greatly altered, but there was no interaction
between Gln186 and Thr342 due to the main-chain conformational
change in the 340-343 residues. The NE2 atom of Gln186 formed a
hydrogen bond with the O4 atom of Glc(+1) at a distance of 2.9
Å.
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