CONA-BINDING PROTEINS OF THE SPERM SURFACE ARE CONSERVED THROUGH EVOLUTION AND IN SPERM MATURATION

Lectin-binding glycoconjugates present on the surface of spermatozoa a re believed to play a crucial role in sperm maturation, capacitation, acrosome reaction, or sperm-egg interaction. We have studied ConA-bind ing surface proteins on spermatozoa from different mammalian species. First, ConA-binding proteins were isolated from boar spermatozoa by af finity chromatography. ConA-binding ability was confirmed by Enzyme-li nked Lectin assay (ELLA). Monoclonal (MAb436/10) and polyclonal antibo dies were raised against chromatography fractions containing purified ConA-binding proteins of boar spermatozoa. MAb436/10 (IgG(2a)) recogni zes a 40kD ConA-binding antigen. Indirect immunofluorescence on fixed and unfixed boar spermatozoa with MAb436/10 indicated a plasma membran e localization of antigen 436/10 in the acrosomal macrodomain. Intersp ecies crossreactivity with MAb436/10 was found by whole cell ELISA and immunocytochemistry. MAb436/10 cross-reacted with human, horse, guine a-pig, bull, and ram spermatozoa in both assays. Expression of ConA-bi nding antigen 436/10 on guinea pig sperm surface was detectable during spermiogenesis and in early stages of sperm maturation. Change of reg ionalization of the antigen did not occur during the epididymal passag e. ConA-binding antigen 436/10 was also detectable in testis and cauda l segments of the epididymis. These findings suggest that ConA-binding proteins located in the acrosomal region are highly conserved through evolution as well as in sperm maturation indicating an important role for the physiology of spermatozoa.