Fig. 4.

Effect of Mg²⁺ on MH/CNM-associated RyR1 mutants. Mg²⁺-dependent changes in the activities of wild-type and mutant RyR were determined at 100 μM Ca²⁺ by the [³H]ryanodine binding method. Activities of wild-type RyRs (A), S2–S3 loop mutants (B), S4–S5 loop mutants (C), and EF-hand mutants (D) are shown. Dotted and dashed lines in B, C, and D are mean values of WT-RyR1 and WT-RyR2, respectively. The smaller dotted line indicates the level at 100%. *P < 0.05 compared with control (-Mg²⁺) by one-way ANOVA. In B, *P < 0.05 for F4732D, G4733E, R4736W, and R4736Q mutants; **P < 0.05 for G4733E mutant. Data are shown as means ± SE (n = 4–6). E: IC₅₀ values of WT-RyR1, EF-hand mutants, and S4–S5 loop mutants are shown. *P < 0.05 compared with WT-RyR1 by one-way ANOVA followed by Tukey’s test. Data are shown as means ± SE (n = 4–5).