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Figure 1.
The TolC Outer Membrane Protein and Its Partial Opening (A) A
side view of the TolC homotrimer (1EK9). (B) A schematic of the
mutations that were studied here to stabilize channel opening. A
network of charged interactions maintaining the resting closed
state of TolC (1EK9). These include Y362, R367 from H7/H8, which
are coordinated by T152, and D153 from H3/H4. Y362 has been
mutated to F and R367 to E to disrupt the network of salt
bridges (shown in bold). The protomers are colored red, blue,
and green. (C) Crystal structures of the open and closed states.
The view is along the trifold axis at the periplasmic,
AcrB-engaging end of the TolC trimer. (D) Helical movements from
the open to the closed state for the two crystal forms.
Transition of the mobile helices H7/H8 from closed state
(orange) to open as exemplified by the different subunits of C2
(cyan and green) and P2[1]2[1]2[1] (gray and yellow). The view
is of overlays of helical fragments H7/H8 (foreground) and H3/H4
(background), revealing the minimal relative movement of H3/H4
static helices as compared with H7/H8. (E) Top view of the same
overlays shown in (D). The displacement of the H7 helix is up to
11 A in the C2 structure. Note also the lagging of the H8
helices and the relative swing of the H7 in respect to H8. The
triangle indicates the molecular trifold axis. Mol Cell. 2008
April 11; 30(1): 114–121. doi: 10.1016/j.molcel.2008.02.015.
Copyright [copyright] 2008 ELL & Excerpta Medica
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