The effect of expression of Munc18-1 mutants on the fusion pore dwell-time. A, Representative reversible transient fusion events, observed in the Im trace. B, The average fusion pore dwell-time increased significantly in cells transfected with Munc18-1 P242S and E466K, compared with controls (p = 0.04 and 0.005, respectively). Cells transfected with Munc18-1 R39C exhibited no differences in the average pore dwell-time, compared with cells transfected with Munc18-1 WT. Numbers above the error bars indicate the number of analyzed patches (samples in statistical analysis) and reversible steps (in parentheses).