Figure 5.

Luminal Ca²⁺ regulation of RyR2 channels by the CSQ2-R33Q and CSQ2-L167H mutants. Mutant CSQ2 (0.5 μg/ml) was added to the luminal side of previously CSQ2-stripped channels. Cytosolic free Ca²⁺ concentration was 1 μM and luminal Ca²⁺ was titrated from 10 μM to 10 mM. Holding potential was 0 mV and the luminal solution contained 100 mM Cs⁺. (A) Example channel recordings with CSQ2-R33Q (left) or CSQ2-L167H (right) present are shown (zero current level marked). (B) Summary Po results. The CSQ2-R33Q data (triangle) was collected on eight different channels. The CSQ2-L167H data (inverted triangles) was collected on eight different channels as well. Dotted line represents CSQ2-WT result presented in Fig. 2 B.