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Figure 2.
Figure 2. Interactions between FPP pyrophosphate head group
and the nearby amino acids in the active side. In A, the
pyrophosphate of FPP (F1) is hydrogen-bound to the backbone NH
and side chain of R30, and backbone NH of G29 as well as the
side chains of R39 and N28. Oxygen and nitrogen atoms are shown
as red and blue dots, respectively. All of the distances of
possible hydrogen bonds are indicated in Å, shown with red
dotted lines. In B, side chain of D26 forms hydrogen bonds with
the backbone NH of Gly27 and the side chain of R194 with the
distances indicated in Å. Moreover, R194 interacts with R200,
which is hydrogen-bound to E198. The segments of UPPs containing
residues 23-43 and 192-205 are represented by the red ribbon.
(C) Superimposition of the  A strand and
three  -helices ( 1, 2, and 3) in the
active-site area from the closed and open conformations of UPPs.
The 2 helix is
shown in red in the closed conformer and purple in the open
conformer. Several amino acids including L85, L88, F89, and W91
on this helix become closer to the bound FPP compared to their
positions (L85', L88', F89', and W91') in the open form. In D,
the Mg2+ (shown in yellow) near IPP is coordinated with H199
from A subunit, E213 from B subunit, and four waters. The
hydrocarbon parts of FPP and hypothetical IPP are represented by
ball-and-stick in yellow and black, respectively. The oxygen and
phosphate atoms in the pyrophosphate moiety are shown in red and
purple, respectively. The segments of A subunit of UPPs 23-43
and 192-205 are represented by red ribbon, and segments of B
subunit of apo-UPPs 210-215 by cyan ribbon.
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