This protein is supposed to help spermatozoa undergo functional maturation while they move from the testis to the ductus deferens. Interacts with A1BG (By similarity). Interacts with KNG1 isoform LMW. Stored in secretory granules of granular convoluted tubules cells. Expressed in submandibular gland. Exponential increase between days 25 and 30 after birth. By androgens. Belongs to the CRISP family.