Figure 2.
FIGURE 2. Electron density maps 2F[0] - F[C] contoured at
0. 7 for the thrombin mutant
C191A/C220A in its free CCF (A) and PPACK-bound CCB (B) forms.
Shown is the region around the mutations (arrows) with the
adjacent 186 loop, the 217–220 strand, the primary specificity
pocket up to the catalytic Ser-195 and His-57. Removal of he
Cys-191–Cys-220 disulfide bond increases exposure of Asp-189
to solvent. Note the flip of the backbone O atom of Gly-219 in
the CCF structure. The O atom of Ser-195 is
oriented away from His-57 in CCF, as seen in the slow form of
wild type (22). Disorder in the side chains of residues in the
186-loop and around Glu-217 and Gly-219 in the CCF structure (A)
is corrected by the presence of PPACK (stick model in green) in
the CCB structure (B). Disorder in the Na^+ binding site (186
and 220 loops) suggests that the conformation of CCF is unable
to bind Na^+, in agreement with functional data on the mutant.
The above figure is reprinted
by permission from the ASBMB:
J Biol Chem
(2007,
282,
27165-27170)
copyright 2007.
for the thrombin mutant
C191A/C220A in its free CCF (A) and PPACK-bound CCB (B) forms.
Shown is the region around the mutations (arrows) with the
adjacent 186 loop, the 217–220 strand, the primary specificity
pocket up to the catalytic Ser-195 and His-57. Removal of he
Cys-191–Cys-220 disulfide bond increases exposure of Asp-189
to solvent. Note the flip of the backbone O atom of Gly-219 in
the CCF structure. The O 
atom of Ser-195 is
oriented away from His-57 in CCF, as seen in the slow form of
wild type (22). Disorder in the side chains of residues in the
186-loop and around Glu-217 and Gly-219 in the CCF structure (A)
is corrected by the presence of PPACK (stick model in green) in
the CCB structure (B). Disorder in the Na^+ binding site (186
and 220 loops) suggests that the conformation of CCF is unable
to bind Na^+, in agreement with functional data on the mutant.