Calcium sensor that participates in triggering neurotransmitter release at the synapse (PubMed:11242035). May have a regulatory role in the membrane interactions during trafficking of synaptic vesicles at the active zone of the synapse (PubMed:7961887). It binds acidic phospholipids with a specificity that requires the presence of both an acidic head group and a diacyl backbone. A Ca(2+)-dependent interaction between synaptotagmin and putative receptors for activated protein kinase C has also been reported. It can bind to at least three additional proteins in a Ca(2+)-independent manner; these are neurexins, syntaxin and AP2. Plays a role in dendrite formation by melanocytes (By similarity). Binds 3 Ca(2+) ions per subunit. The ions are bound to the C2 domains. Homotetramer (Probable). Interacts with SCAMP5 (By similarity). Interacts with STON2 (By similarity). Forms a complex with SV2B, syntaxin 1 and SNAP25 (PubMed:15466855). Interacts with SV2A, SV2B and SV2C (By similarity). Interacts with RIMS1 (By similarity). Interacts with PRRT2 (PubMed:27052163). Interacts with DNAJC5 in a phosphorylation-dependent manner (By similarity). Interacts (via N-terminus) with RAB3A (By similarity). Interacts with SYT12 (By similarity). Interacts with calmodulin (By similarity). Expressed in the brain and adrenal medulla (at protein level). Detected in the brain at 18 days post coitum (dpc) (at protein level). Expression increases after birth, with expression increasing till adulthood. The first C2 domain mediates Ca(2+)-dependent phospholipid binding. The second C2 domain mediates interaction with SV2A and probably with STN2. Glycosylated. Belongs to the synaptotagmin family.