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Figure 4.
Fig. 4. Diminished axial-stagger asymmetry in the N-terminal
region of scallop S2 (red solid lines) relative to human cardiac
S2 (blue dashed lines). Axial staggering may therefore not be a
general inducer of nonequivalence of S1 heads in off-state
structures of myosin (see Discussion). The difference between
these isoforms in the axial staggering between the helices is
most extensive for those structures (darkest shades) with the
highest order nearest the N-terminus. Stagger at any residue is
calculated from output of LSQAB^28 from the CCP4 program
suite,^29 in which 7-residue-long segments of the two helices of
a coiled coil are fitted. The axial staggers are calculated for
the N-terminal regions of five crystallographically independent
scallop S2 coiled coils (from the C2 space group and the two
coiled coils from each of the P2[1]2[1]2[1] and P2[1] space
groups) and of three crystallographically independent human
cardiac S2 coiled coils (one wild type and two coiled coils in
which a residue outside the measured region was mutated) (see
Ref. 21).
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