Detection of sperm coating antigens immunologically related to a seminal protein in rat

We report in this paper that proteins from the surface of ejaculated spermatozoa contain antigenic determinants cross-reacting with a rabbit antiserum raised against native CFS, a protein secreted from the rat seminal vesicle and composed of two subunits, namely RSV IV and RSV V. Conversely, no such proteins could be extracted from cauda epididymal spermatozoa. The cross-reacting proteins derived from the ejaculated spermatozoa were analyzed by SDS-PAGE. An electrophoretic pattern different than that expected for native CFS in denaturing conditions was found. In vitro reconstitution experiments showed that labeled native CFS is able to bind cauda epididymal spermatozoa. The CFS protein recovered from the sperm surface was examined and alterations of its structure were also noted. The sperm-coating abilities of CFS and of its RSV IV subunit are discussed.