Fig. 6. Effect of Q/R mutations in SNAP-25 on the extent of exocytosis in PC12 cells. PC12 cells were transfected with a plasmid-encoding growth hormone along with control plasmid, plasmid encoding Em2 or plasmid encoding Em2 containing the double Q/R mutations. After 3 days the cells were permeabilised, treated with BoNT/E for 40 minutes and responses to 0 or 10 µM Ca²⁺ determined. (A) GH release shown as a percentage of total GH expressed. (B) Immunoblot with anti-HA showing the expression of Em2 and the double Q/R mutant in the same cells used for the GH assay.