Figure 5. Conformational transition of O. cuniculus sarcoplasmic Ca²⁺-pump (SERCA).

(a) Crystallographic E1-Ca²⁺ bound open (2c9m) and E1-Ca²⁺- nucleotide bound (1t5s) state, showing the headpiece domains coloured in red (A), blue (P) and green (N) and the TM helices in brown. (b) Principal components of the X-ray ensemble (65 structures) describe the E2->E1 pumping transition (PC1) and the closing of the headpiece (PC2). (c) Left: projections of the X-ray ensemble structures and the eBDIMS trajectories onto the PC1-2 subspace; PC2 separates the crystal structures into open (red) and closed (blue); the reconstructed structure 4nab is shown as a red dot. Right: comparison between the forward pathways computed by eBDIMS, iENM, NOMAD-Ref, MinActionPath and Climber. Reverse pathways generated by eBDIMS, iMODS, NMSIM and Climber also shown. (d) rMSD and PC1-2 distance between the forward trajectory and two crystallographic intermediates.