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Figure 3.
FIGURE 3. Hormone binding to CBG. A, stereo representation
of the CBG (blue) steroid-binding site. B, schematic depiction
of the interactions between CBG and cortisol. Water molecules
are shown as red dots, hydrophobic interactions are shown with
dashed lines, and polar interactions are shown with dotted lines
in A and B. C, for comparison, thyroxin-binding site in TBG
(Protein Data Bank code 2ceo). Note that similar residues are
involved in binding cortisol in CBG and thyroxin in TBG. D,
mapping of three different serpin ligand-binding sites onto the
CBG surface (in blue). Cortisol is shown in yellow, and thyroxin
is in green, as bound to TBG. Heparin (in orange) binds on top
of helix D in antithrombin (Protein Data Bank code 1e03) close
to the shared ligand-binding site in TBG and CBG.
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