Fig. 5.

Verification of interaction between tryptophan and isoleucine in the putative caffeine-binding site. a Schematic diagrams of four mutants at W4644 and/or I4925 with expected interactions and movement of the CTD. Light pink in I4925A and W4644A_I4925A indicates location of the CTD in WT. b–e Ca²⁺-dependent [³H]ryanodine binding to W4644I (b), W4644L (c), I4925A (d) and I4925A_W46444A (e) in the presence (closed circles) and absence (open circles) of 10 mM caffeine. Data are given as mean ± SEM (n = 4). f Summary of pCa₅₀ values of WT and the mutants with (hatched columns) or without (open columns) 10 mM caffeine. Data are given as mean (horizontal bar) and individual values (circles). * and *** indicate statistical significance with p = 0.004 and p < 0.0001, respectively, vs WT using one-way ANOVA followed by Dunnett’s post hoc test. ### indicates p < 0.0001 vs control using unpaired two-tailed Student’s t-test