Identification and preliminary characterization of a sperm-binding protein in normal human semen

In the seminal plasma of normal men a protein, immunologically related to a major protein (RSV-IV) secreted from the rat seminal vesicle epithelium, was detected by competition with RSV-IV in a specific radioimmunoassay using a rabbit anti RSV-IV antiserum. The protein was partly (80%) purified by column chromatography; characterization by gel electrophoresis indicated that the protein is slightly basic and has a molecular weight of 140 000. The protein was present on the surface of human spermatozoa as well as in the ejaculates of azoospermic men and it is believed to be a sperm-binding protein.