Purification and characterization of PSP-I and PSP-II, two major proteins from porcine seminal plasma

Two major glycoproteins, designated PSP-I and PSP-II, were purified from porcine seminal plasma by ammonium sulfate fractionation, CM-cellulose chromatography, gel filtration on Sephadex G-75 (superfine), and reverse phase high performance liquid chromatography. These two proteins exist in several forms differing mainly in the carbohydrate moiety. The complete amino acid sequence of PSP-I has been determined by automated Edman degradation of peptides generated by proteolytic digestion and cyanogen bromide cleavage. The protein is 109 residues long and has a single glycosylation site at the asparagine residue at position 47. In addition, the N-terminal sequence of PSP-II has also been determined. PSP-I is a unique protein; a sequence homology search using the protein data base did not reveal any significant homology with other proteins. PSP-II shares 50% sequence homology with a family of zona pellucida-binding glycoproteins at the N-terminus.