Plays a role in acrosome compaction and sperm morphogenesis. Is implicated in sperm-oocyte interaction during fertilization. First localized in acrosome granule, later migrates to the inner and outer acrosomal membrane. Released after the acrosomal reaction. Expressed in testis. Detected in sperm cells. N-glycosylated. Belongs to the zona pellucida-binding protein Sp38 family.