Potentially involved in docking of synaptic vesicles at presynaptic active zones (PubMed:7901002). May mediate Ca(2+)-regulation of exocytosis acrosomal reaction in sperm (By similarity). Interacts with OTOF. Interacts with SYT6 and SYT8; the interaction is Ca(2+)-dependent (By similarity). Cerebral cortex, hippocampus, cerebellum, and adrenal medulla. Phosphorylated by CK2. (Microbial infection) Targeted and hydrolyzed by C.botulinum neurotoxin type C (BoNT/C), which hydrolyzes the 252-Lys-|-Ala-253 bond (PubMed:7737992). Cleavage inhibits neurotransmitter release (PubMed:7901002). Belongs to the syntaxin family.