Fig. 3. Effect of Q/E mutations in SNAP-25 on the time course and Ca²⁺-dependency of exocytosis in PC12 cells. The cells were transfected with the GH plasmid along with the Em2 plasmid or Em2 harbouring the double Q/E mutations. After 3 days, the cells were permeabilised with digitonin and treated with BoNT/E light chain followed by incubation with Ca²⁺ to stimulate exocytosis. (A) Time course of GH release in response to 10 µM Ca²⁺ from cells co-transfected with either Em2 or the double mutant. (B) Ca²⁺-dependency of GH release from cells transfected with Em2 or the double Q/E mutant.