Potentially involved in docking of synaptic vesicles at presynaptic active zones. 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). Colocalizes with Lamin A/C and NuMA in interphasic nuclei, and with NuMA and gamma-tubulin in the pericentrosomal region of the mitotic spindle in dividing cells. Phosphorylated by CK2. The disease is caused by variants affecting the gene represented in this entry. The glycine-rich C-terminus serves as an unconventional nuclear localization signal. Belongs to the syntaxin family.