Extended Data Figure 9. The putative cytosolic Ca²⁺ sensor in InsP₃R1.

a, Cut-open side view of the cryo-EM density map of InsP₃R1 is shown with the structures of the Ca²⁺ sensor region for InsP₃R1 (residues 1952–2270) and RyR1 (residues 3877–4251; PDB accession 3J8H); the EF-hand of RyR1 includes residues 4071–4130. b, Close-up view of the overlapped Ca²⁺ sensor structures for InsP₃R1 (colour-coded by domain as in Fig. 1) and RyR1 (tan). The conserved Glu2101/InsP₃R1 and Glu4032/RyR1 are shown in red. c, Sequence alignment of the predicted Ca²⁺ sensor regions comprising the conserved Glu2101/InsP₃R1 and Glu4032/RyR1 (red) (rInsP₃R1/GI code:17380349; hInsP₃R1/GI code: 519668682; hInsP₃R2/GI code: 259016258; hInsP₃R3/GI code: 209572633; RyR1/GI code: 134134; RyR2/GI code: 308153559; RyR3/GI code: 75074791); green highlight denotes completely conserved residues; yellow highlight denotes identical residues.