FKBP1B and catecholaminergic polymorphic ventricular tachycardia: We observed that RyR2-S2808D totally depleted of calstabin-2 is in a primed state comparable to the CPVT mutants, consistent with leaky arrhythmogenic RyR2 channels (RMSD = 0.30, Fig. 1c,e-g).