Figure 5. Effects of DP4 and DP4-mut on [³H]ryanodine binding to RyR1_N and RyR1_MHS.

Experiments were carried out as described in Figure 2 with 0–500 μM DP4 (closed symbols) or DP4-mut (open symbols) at 30 μM free Ca²⁺. Circles, RyR1_N; triangles, RyR1_MHS. Note that DP4 greatly activated RyR1_N in a concentration-dependent manner, whereas it produced only small activation of RyR1_MHS. DP4-mut had little activating effects. Results are means±S.E.M. (n=3–4).