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Figure 2.
FIG. 2. E217K thrombin is inactive because of the altered
hydrogen bonding of the active site residues. a, stereo
representation of the electron density surrounding residues
His-57, Trp-60d, 191-196 and 215-220. The conformation of this
region is significantly altered for the E217K variant, and as a
result of the movement of Glu-192, the hydrogen bonding of the
catalytic residues has become non-catalytic. b, superposition of
the catalytic residues (His-57 and residues 192-195) of E217K
(yellow) and wild-type, active thrombin (1HAH [PDB]
, magenta) illustrates the new hydrogen bonding pattern (green
broken lines) and the consequent loss of the oxyanion hole,
normally formed by the amide hydrogens of Gly-193 and Ser-195
(arrows). The amide hydrogen of Gly-193 is oriented away from
the oxyanion hole, and the amide hydrogen of Ser-195 is
hydrogen-bonded to the main chain oxygen of Glu-192. The
hydrogens of Ser-195 are shown for clarity (white).
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