May have a regulatory role in the membrane interactions during trafficking of synaptic vesicles at the active zone of the synapse. It binds acidic phospholipids with a specificity that requires the presence of both an acidic head group and a diacyl backbone. Binds 3 Ca(2+) ions per subunit. The ions are bound to the C2 domains. Homodimer or homotrimer (possible). Synaptic vesicles in neurons. Spinal cord, brainstem, midbrain and electric organ. Belongs to the synaptotagmin family.