|
Figure 5.
Fig. 5. The transition state of the IIA^Mtl-P-HPr
complex. A, detailed view around the active site histidines,
illustrating the backbone and side chain positions in the
unphosphorylated complex, the dissociative transition state, and
the associative transition state. The backbones of IIA^Mtl and
HPr are shown in dark blue and dark green, respectively, for the
unphosphorylated complex, and in light blue and light green,
respectively, for the putative dissociative and associative
transition states; the active site histidines and
pentacoordinate phosphoryl group (in the case of the transition
states) are shown in purple for the unphosphorylated complex, in
red for the dissociative transition state (N  2-N  1 distance
of ~6 Å between His-65 and His-15), and in orange for the
associative transition state (N 2-N 1 distance
of ~4 Å between His-65 and His-15). Small changes in the
backbone of residues 64-66 of IIA^Mtl and residues 14-16 of HPr
are required to accommodate the transition states. B, detailed
view of the active site in the putative transition state
illustrating the interactions that stabilize the phosphoryl
group. The color coding is as follows: the backbone and side
chains of IIA^Mtl are shown in blue and red, respectively; the
backbone and side chains of HPr are shown in green and gray,
respectively; the active site histidines are in purple, and the
pentacoordinate phosphoryl group is in yellow. Residues from HPr
are labeled in italics.
|
