Figure 2.

Conformational changes of the individual domains between C1 and C4 conformers. (A) Structural comparison between C1 (gray) and C4 (violet) protomers. The two tetrameric structures are superimposed relative to the channel domain. The violet arrows indicate the conformational changes from C1 to C4. The same is applied to the other panels. (B) Structural shifts of the corona between C1 and C4 tetramers. The outskirt of the corona, composed of the Handle and Helical domains, moves towards the SR lumen from C1 to C4. Shown here is a side view. (C) The NTD undergoes a rocking motion with the central domains A and B upwards and the outer domain C downwards. For visual clarity, only two diagonal protomers are shown in side view. (D, E) The Central (D) and channel (E) domains remain nearly unchanged between C1 and C4 states. All structure figures were prepared with PyMol⁴⁸.