Predicted to enable syntaxin binding activity. Involved in several processes, including positive regulation of dendrite development; regulation of pole plasm oskar mRNA localization; and secretion by cell. Located in cytosol and terminal bouton. Is extrinsic component of cytoplasmic side of plasma membrane. Is expressed in several structures, including central nervous system; garland cell; gonad; nerve; and sensory nervous system primordium. Human ortholog(s) of this gene implicated in West syndrome; developmental and epileptic encephalopathy 4; and familial hemophagocytic lymphohistiocytosis 5. Orthologous to several human genes including STXBP1 (syntaxin binding protein 1).