Involved in the trafficking and exocytosis of secretory vesicles in non-neuronal tissues. Mediates Ca(2+)-regulation of exocytosis acrosomal reaction in sperm. May mediate Ca(2+)-regulation of exocytosis in insulin secreted cells (By similarity). Homodimer or homooligomer. Homodimerization and homooligomerization do not depend on Ca(2+). Interacts with SYNCRIP isoform 2 C-terminus. Binds inositol 1,3,4,5-tetrakisphosphate (IP4). Binds to AP2 in a Ca(2+)-independent manner. Interacts with STX1A, STX1B and STX2; the interaction is Ca(2+)-dependent (By similarity). Ubiquitous. Strongly expressed in heart, kidney, cerebral cortex, pancreas, and many insulin-secreting cells; lower expression in spleen. Broadly distributed in kidney. The first C2 domain/C2A does not mediate Ca(2+)-dependent phospholipid binding. The second C2 domain/C2B is responsible for SYNCRIP and inositol 1,3,4,5-tetrakisphosphate (IP4)-binding. Belongs to the synaptotagmin family. Truncated N-terminus.