ISOLATION OF AN IMMOBILIZING ANTIGEN FROM RABBIT SPERM MEMBRANES

A method was described for isolation of individual sperm antigens from rabbit sperm membranes. Three fractions were prepared by centrifugation of a rabbit epididymal sperm homogenate, examined by sodium dodecyl sulfate polyacrylamide disc gel electrophoresis and by EM, and tested for hyaluronidase and succinic dehydrogenase activity. The membrane-rich fraction was extracted with lithium diiodosalicylate and a sperm surface membrane glycoprotein (MGP; immobilizing antigen) isolated from it by ion-exchange chromatography. The MGP showed a single immunodiffusion precipitin band against goat anti-rabbit sperm globulin. Antibodies to MGP immobilized rabbit sperm in the presence of complement. This MGP-immobilizing antigen was localized on the head and tail plasma membrane of epididymal, ejaculate and capacitated sperm by exchange agglutination and immobilization in the presence of guinea pig complement.