Purification of GP-83, a glycoprotein secreted by the human epididymis andconjugated to mature spermatozoa

Epididymal secretions are critical for mammalian spermatozoa to acquire bot h forward motility and an ability to recognize and penetrate oocytes. Previ ous studies identified two glycoproteins, GP-83 and GP-39, which were secre ted by the human epididymis and may be related to maturation of sperm funct ion. In this study, GP-83 was purified from human seminal fluid by DEAE-ion exchange, gel filtration chromatography and preparative gel elution. The i soelectric point (pl) of purified GP-83 was 6.57, Monospecific antiserum to GP-83 was induced in male New Zealand rabbits and confirmed on immunoblots , GP-83 was found in fluid, tissue and sperm extracts of corpus and cauda e pididymis, bur not in the caput. Immunohistochemical localization identifie d GP-83 in the luminal contents and in the supranuclear region and cell mem brane of principal cells of the corpus and cauda epididymis. GP-83 was foun d on the anterior acrosome in ejaculated spermatozoa, and shifted to the eq uatorial region after capacitation and the acrosome reaction.