Functions in exocytosis in pancreatic acinar cells regulating the fusion of zymogen granules with each other. May have a pore-forming activity on membranes and regulate exocytosis in other exocrine tissues (By similarity). Monomer and homooligomer; most probably hexameric. Interacts with GP2 (By similarity). Associated in a cholesterol-dependent manner with lipid rafts of zymogen granule membranes. Contains intrachain disulfide bonds.