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Figure 4.
Figure 4. Disruption of intra-ring contacts between the
equatorial domains of the trans ring. (a) The interface
between neighboring equatorial domains in the trans ring of the
ATP-bound complex. The EM-derived electron density is shown as a
gold mesh, with the adjacent equatorial domains in blue and
magenta. In the ATP complex (and all crystal structures of GroEL
complexes), two  -strands
from each subunit form a four-stranded -sheet
that is a major contact holding the ring of equatorial domains
together (highlighted by a black rectangle). (b) The
corresponding view of the ADP-bound complex (with EM density
shown as a blue mesh and equatorial domains in green and orange)
shows that a small (  3°)
rotation of the equatorial domain results in the two strands
from the orange subunit moving upward (in this view) and the two
strands from the green subunit moving downward, pulling apart
the -sheet
contact. (c,d) Structure of the rear half of the ring of
equatorial domains from the ATP-bound (c) and ADP-bound (d)
complexes. The seven-fold axis is vertical and in the image
plane, and these views are reached by tipping a and b forward by
30°.
(e) A comparison of the intra-strand (main chain) distances in
the ATP (blue and magenta) and ADP (green and gold) complexes,
showing that the strand separation increases by 4–5 Å
upon ATP hydrolysis.
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