Figure 1.

Synaptotagmin C₂B polylysine region is highly conserved throughout evolution and is required for efficient synaptic transmission. (A) ClustalW sequence alignment of 56 highly conserved amino acids from the C₂B domain of synaptotagmin. Bars indicate β-sheets within the C₂B domain. Circles mark the Ca²⁺-binding motif. Dotted line denotes the polybasic region. Asterisks mark the polylysine motif. (B) Representative traces showing evoked release during 0.05-Hz stimulation in HL3 saline containing 1.5 mM Ca²⁺ in transgenic controls (−/−;P[syt^WT]) and polylysine motif mutants (−/−;P[syt^KQ]). Each trace is an average of 10–12 individual traces from a single muscle fiber. Stimulus artifact has been removed for clarity. (C) The mean EJP amplitude in saline containing 1.5 mM Ca²⁺ was 14.2 ± 0.82 mV (mean ± SEM; n = 34 fibers) for polylysine motif mutants and 32.4 ± 0.99 mV (mean ± SEM; n = 42 fibers) for transgenic wild-type controls (p ≪ 0.001).