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Figure 1.
Fig. 1. The structure of S. agalactiae hyaluronate lyase
with bound hexasaccharide hyaluronan substrate. A, ribbon
drawing of the structure of the complex. All three domains of
the enzyme are shown, the N-terminal  -sheet
domain ( II-domain,
top), the  -helical
domain ( -domain,
middle), the C-terminal -sheet
domain ( II-domain,
bottom), as well as the cleft with the bound hexasaccharide unit
of hyaluronan substrate (depicted in a ball and stick fashion
with bonds colored in red). The structure of the enzyme is
color-coded by the secondary structure elements ( -helices in
blue, 3[10] helices in purple, -sheets in
green), and the atoms of the substrate are colored by the atom
type (carbon atoms in green, oxygen atoms in red, and nitrogen
atoms in blue). Consecutive disaccharide units of HA starting
from the reducing end are labeled as HA1 , HA2, and HA3. B,
comparison of structures of S. agalactiae and S. pneumoniae
hyaluronate lyases. The S. agalactiae enzyme (black) (domains
labeled) has an additional domain at its N terminus ( I-domain).
The cleft area in this enzyme is also wider than that of the S.
pneumoniae hyaluronate lyase (blue) (maximum difference in width
of ~7 Å). C, electrostatic potential distribution in the
catalytic cleft. The positive potential is shown in blue and the
negative potential in red. The majority of the cleft is highly
positively charged (middle and the left side; positive patch)
whereas at the product-releasing end of the cleft is negatively
charged (right side of the cleft; a negative patch). The
hydrophobic patch is also shown. Bound hexasaccharide hyaluronan
is shown as sticks color-coded by atom type. Reducing and
non-reducing ends of HA are labeled.
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