CALM1 and catecholaminergic polymorphic ventricular tachycardia: To analyse the effect of CPVT-associated mutations on CaM–RyR23583-3603 interaction, we carried out isothermal titration calorimetry (ITC) experiments in the absence (5 mM EGTA) and presence of activating Ca2+ concentration (5 mM CaCl2).