Figure 9. Conformational transition between E1.2CA²⁺ and E1.ATP states of the Sarcoplasmic Reticulum Ca²⁺-ATPase (SERCA).

A. Structures of the (left, PDB ID: 1SU4) and the E1.ATP (∼E1P) (right, PDB ID: 1T5S) states. The P, A and N domains are shown in blue, red and green respectively. Rest of the protein including the transmembrane domain is shown in gray. The central structure is the trace of the transition state produced by ANMPathway. B. The energy of the system along the transition. Total number of images in the pathway is 106, RMSD between two consecutive images is ∼0.2 Å. The transition state corresponds to image 74. C. Cumulative squared cosines between the structural change to reach a few selected conformers/images along the transition pathway and the ANM modes accessible to the starting ( state) structure.