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Figure 4
Stereographic projections of the κ = 180° section of the self-rotation functions from (a) a 13-mer parallel β-barrel, (b) a tridecameric α-barrel from PDB entry 2x2v and (c) the refined superhelical TIF2 structure. The molecules in (a) and (b) were aligned with the NCS axis at ω = 40°, φ = 0° to facilitate comparison with the diffraction data (Fig. 3a) and the final model in (c). The regular barrels have more internal symmetry elements than the true structure. Of note is the presence of the 13-fold NCS axis in this κ section, but its absence in the correct structure in (c). Calculations were done as in Fig. 3(a) except that for the representations (a) and (b) the initial contour levels were raised to 90% and 70% of the C2 crystallographic peak in order to better visualize the twofold axes.

IUCrJ
Volume 2| Part 2| January 2015| Pages 177-187
ISSN: 2052-2525
doi:10.1107/S2052252515000238