Plays a role in acrosome expansion and establishment of normal sperm morphology during spermatogenesis (By similarity). Important for male fertility (PubMed:11870081). Primarily found in the equatorial segment of the acrosome (PubMed:11870081). The tyrosine phosphorylated protein localizes to a smaller region within the equatorial segment (By similarity). Also expressed weakly in the principal segment (PubMed:11870081). Testis specific. N-glycosylated.