[Correlation of epididymal protease inhibitor Eppin and Semenogelin on human ejaculated spermatozoa]

To evaluate the correlation of epididymal protease inhibitor(Eppin) and Semenogelin(Sg) on human ejaculated spermatozoa.

The experimental approaches include: (1) Immunoprecipitation of Eppin with anti-Eppin from semen; (2) Colocalization of Eppin and Sg by immunofluorescence; (3) Immunoprecipitation of rEppin and rSg;(4) Far-Western blotting of rEppin and rSg;(5) Competition of saturated 125I-rSg binding to rEppin with unlabeled Sg, and direct binding of 125I-rSg to rEppin on a blot; (6) Autoradiography of 125I-rSg with rEppin.

Eppin-Sg complex present on the surface of human ejaculated spermatozoa, Cys-239 is the only cystein for rEppin binding rSg. Reduction and carboxymethylation of Cys-239 blocks binding of 125I-rEppin to rSg.

Our study demonstrates that Eppin and Sg bind to each other on human ejaculated spermatozoa. A disulfide linkage occurs between Sg and Eppin, indicating the specificity of binding.