Fig. 4: Structural details of hSPCA1 in the CaE2P and early E2P states.

a Atomic models (color ribbon) and cryo-EM densities (dark gray mesh, contoured at 7.0 σ) of hSPCA1 in the CaE2P and early E2P states. The cryo-EM densities of BeF₃^–, Mg²⁺, Asp350, and Asp644 of hSPCA1 in the CaE2P and early E2P states are shown (black mesh, contoured at 10.0 σ). b Structural comparison of hSPCA1 cytoplasmic domains in the CaE2P (color) and CaE1P-ADP (dark gray) states by global alignment. c The movement of the ¹⁸⁹TGE and ³⁵⁰DKT motifs from the CaE1P-ADP state to the CaE2P state. The black dashed lines show the distance between Cα of Asp350 in the CaE1P-ADP state and that in the CaE2P state, and the distance between Cα of Glu191 in the CaE1P-ADP state and that in the CaE2P state. The deep red dashed line shows the distance between Cα of Glu191 and Cα of Asp350 in the CaE2P state. d The conserved ¹⁸⁹TGE motif (hot pink) in the CaE2P state and the ADP molecule (dark gray) in the CaE1P-ADP state. e Structural comparison of hSPCA1 TMD in the CaE2P (color) and CaE1P-ADP (dark gray) states. The red text shows the distance from the Cα of Leu96 in the CaE1P-ADP state to the Cα of Leu96 in the CaE2P state. f Structural comparison of hSPCA1 in the early E2P (color) and CaE2P (dark gray) states by global alignment. g Structural comparison of the ¹⁸⁹TGE and ³⁵⁰DKT motifs in the early E2P (color) and CaE2P states (dark gray). h Structural comparison of hSPCA1 TMD in the early E2P (color) and CaE2P (dark gray) states. i Structural comparison of hSPCA1 TM4 and TM6 in the early E2P (orange-red) and CaE2P (dark gray) states by alignment of TM4 and TM6. The black dashed lines (right) show the distances from the Ca²⁺ ion (dark gray sphere) in the CaE2P state to the main-chain carbonyl oxygen atoms of Val303, Ala304, and Ile306, and the side-chain oxygen atoms of Glu308, Asn738, and Asp742.