Disease-associated mutations in the NTD RYR1. (A) Cryo-EM structure of RYR1 tetramer viewed from the cytoplasmic side (PDB accession no. 5TB0). The crystal structure of the RYR1 NTD (PDB accession no. 2XOA; Tung et al., 2010) focused on in this study (dashed box) is superimposed on the cryo-EM structure. Each domain in the crystal structure of the NTD (dashed box) in one monomer is colored in blue (A domain), green (B domain), and red (C domain), respectively. The part corresponding to the NTD in the remaining monomers is shown in cyan. Within one monomer of the cryo-EM structure, the domains corresponding to SPRY1, P1, SPRY2, and SPRY3 are shown in light green; the domains corresponding to Handle, HD1, P2, and HD2 are shown in yellow-green; and the Central domain is shown in orange. The portion excluding the C domain in the NTDs is shown in light brown. Transmembrane helix S6 constituting the channel pore (dotted circle) is shown in red. (B) Closeup view of the NTD. The three domains are colored the same as in A. The seven mutation sites used in this study (C36, Q156, R164, G249, G342, R402, and Y523) are labeled.