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Figure 8.
Figure 8: Proposed mechanism of gating. a, Crystal structure
of the MthK channel (opened conformation) with subdomains
removed from the gating ring. RCK domains forming a fixed
interface with each other are the same colour. Disordered
linkers are shown as dashed lines and Ca^2+ ions as yellow
spheres. b, Hypothetical model of the MthK channel in its closed
conformation. RCK domain pairs of the same colour were moved as
rigid bodies. The movements decrease the gating ring diameter by
13 Å, allowing the inner helices to achieve the conformation
observed in the KcsA K+ channel (a closed K+ channel). c,
Cartoon outlining the gating motions. A single rigid unit is
shown (red). Arrows show proposed direction of rotation and
translation. Release of Ca^2+ ions (yellow circles) is
associated with conformational changes in the gating ring that
close the channel.
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