Extended Data Fig. 5: Related to Figure 3. SP9 has no effect on vesicle fusion mediated by neuronal SNAREs alone, or by Syt1(QM).

a–c, SP9 has no effect on vesicle fusion mediated by neuronal SNAREs alone. a, Effects of 10 μM of P0 or SP9 on vesicle association. b, Corresponding Ca²⁺-independent fusion probabilities. c, Corresponding average probabilities of Ca²⁺-independent fusion events per second. d–j, the quintuple Syt1(QM) mutant alleviates the inhibitory effect of SP9 on neuronal synaptic vesicle fusion. d, Effect of 10 μM of SP9 on vesicle association (* p = 0.01629). e, Corresponding Ca²⁺-independent fusion probabilities. f, Corresponding average probabilities of Ca²⁺-independent fusion events per second. g, Corresponding Ca²⁺-triggered fusion probabilities. (h–j) Corresponding Ca²⁺-triggered fusion amplitude of the first 1-sec time bin upon 500 μM Ca²⁺-injection (h), the cumulative Ca²⁺-triggered fusion probability within 1 min (i), and the decay rate (1/τ) of the Ca²⁺-triggered fusion histogram (j). The fusion probabilities and amplitudes were normalized to the number of analysed neuronal SV - neuronal PM vesicle pairs (Supplementary Table 2). Panels a, c, d, f, h, i show box plots and data points for n (indicated below each box plot) independent repeat experiments (Supplementary Table 2). Two-tailed Student’s t-tests were used for SP9 vs. No SP. Decay constants (boxes) and error estimates (bars) in panels j computed from the covariance matrix upon fitting the corresponding histograms combining all repeats with a single exponential decay function using the Levenberg-Marquardt algorithm.

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