Fig. 7.

R163C exhibits altered [³H]Ry binding and Ca²⁺ activation, but inhibition by Ca²⁺ and Mg²⁺ remains unaltered. Equilibrium [³H]ryanodine (2 nM) binding to 100 mg/ml SR protein was performed at 37°C for 3 h in the presence of 50 nM to 10 mM Ca²⁺. Free Ca²⁺ was adjusted by EGTA according the software Bound and Determined (Voss et al., 2008). The data points are mean ± S.D. from n = 6 determinations from two independent membrane preparations from paired R163C heterozygous and WT mice. A and B, raw data and corresponding data normalized to the maximum binding within each genotype. C and D, Mg²⁺ (0–20 mM) inhibits equilibrium [³H]Ry binding. The free Ca²⁺ in the reaction mixture was buffered by EGTA. The data points are mean ± S.D. from n = 6 determinations from two independent membrane preparations from paired R163C heterozygous and WT mice.