function:May be involved in packaging and condensation of the acrosin zymogen in the acrosomal matrix via its association with proacrosin.,PTM:Phosphorylated on Tyr residues in capacitated sperm.,PTM:The N-terminus is blocked.,subcellular location:Colocalizes with proacrosin in the acrosome of sperm.,subunit:Binds proacrosin.,tissue specificity:Expression restricted to testis in normal tissue. Expressed in a wide spectrum of cancers, including bladder, breast, liver, lung and colon cancers.,