FIGURE 7.

Effect of V4880A on the luminal Ca²⁺ activation of single RyR2 channels. A and B, single-channel activities of RyR2 WT (A) and V4880A mutant (B) were recorded in a symmetrical recording solution containing 250 mm KCl and 25 mm Hepes (pH 7.4). The Ca²⁺ concentration on the cytoplasmic (cyto) and the luminal face of the channel was first adjusted to ∼45 nm. The luminal Ca²⁺ concentration was then increased to various levels by addition of aliquots of CaCl₂ solution. C, the relationships between open probability and luminal pCa of single RyR2 WT (solid circles) and the V4880A mutant (open circles). The data points shown are mean ± S.E. from five RyR2-WT and four V4880A single channels.