The Proteins of Bovine Seminal Plasma

Experiments have been reported in Paper I (1) in which the proteins of bovine seminal plasma were subjected to preliminary and electrophoretic characterization. In order to characterize this protein system further, ultracentrifugal and immunological methods have been applied. A limited amount of work has been reported on the ultracentrifugation of the seminal plasma proteins. Ross (2) has noted a glycoprotein component in human seminal plasma with a sedimentation velocity of 7 (s~~,~ units), while the proteins of low molecular weight that were present were not observed to sediment under similar conditions. The proteins of seminal plasma have not been well characterized by immunological reactions, although spermatozoa of different species have been studied by this means (3). Ross (2) has summarized some of the earlier investigations on the human seminal plasma proteins and confirmed with precipitin tests that antisera to blood serum may react more strongly with seminal plasma than does antiserum to the seminal plasma itself. Antisera to seminal plasma also reacted less strongly with blood serum than the antisera to the blood serum did with the seminal plasma. Several investigators (2, 4-6) have reported a close relationship of the proteins of human seminal plasma to those of blood serum. In comparing the proteins of bovine seminal plasma with those of blood serum (I), it was found that electrophoretically the majority of these proteins resembled the ar-globulins. Chemical evidence indicated, however, that they probably were not similar. Subsequently it was noted that there was a striking electrophoretic and ultracentrifugal similarity of the proteins of milk serum (non-casein milk proteins) to the proteins of seminal plasma. Consequently, the proteins of bovine seminal plasma have been further characterized and compared with the proteins of blood and milk serum to determine possible relationships.