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Figure 6.
Figure 6. Conformational switch in the EF hands of the N
lobe of TnC. Stereo diagram of the EF-hand domains I (a) and II
(b) in the Ca^2+-free (yellow) and Ca^2+-bound (blue) structures
of the N lobe of TnC. The helices of a domain are reoriented
during the transition by conformational changes occurring in two
hinge regions. The mechanism of the hinges is different, in
EF-hands I and II, however. In particular, the hinge is more
extended near helix B, rather than near helix D; this is because
in EF-hand I, it involves not only residues from the b sheet but
also residues T36-E38 (orange in the Ca^2+-free structure),
which define an additional turn (cyan) of helix B when Ca^2+ is
bound.
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