Fig. 2.

Twofold symmetry. a Superposition of RyR1 Repeat34 domain onto itself via a 180° rotation shows that the domain has a clear intrinsic twofold symmetry. Its original N-terminal region and C-terminal region are displayed in cyan and orange, respectively, and the superposed version is displayed in gray. b Superposition of DBM RyR Repeat34 domain onto itself via a 180° rotation shows that the intrinsic twofold symmetry is compromised by the presence of helix α0′, the difference between helix α1 and helix α1′, and the difference between loop α1-α2 and loop α1′-α2′. Its original N-terminal region and C-terminal region are displayed in pink and blue, respectively, and the superposed version is displayed in gray