Biochemical properties of secretory proteins from rat seminal vesicles

The secretions of rat seminal vesicles from the so-called copulatory plug when getting in contact with the secretions of the coagulating gland. Depending on the sexual activity of the respective animal and the extraction conditions, the protein pattern of the seminal vesicle secretion varies to some extent. We have studied the biochemical properties of the proteins SVS I, SVS II, sulfhydryl oxidase and SVS III-VIII. The most interesting protein is SVS II which is the main substrate of coagulating gland transglutaminase and serves as the most important monomer during semen coagulation. It is highly soluble in acidic solutions. The monomeric polypeptide has a molecular mass of 49 kDa, is glycosylated with fucose, glucose, mannose and N-acetylated sugars and has a highly basic pI of 10.5. Particularly interesting are its functional and structural relationships with actin. It is the first described protein with actin modulating properties that is secreted in an androgen-dependent manner.