LOCALIZATION AND STRUCTURAL CHARACTERIZATION OF AN OLIGOSACCHARIDE O-LINKED TO BOVINE PDC-109 - QUANTITATION OF THE GLYCOPROTEIN IN SEMINALPLASMA AND ON THE SURFACE OF EJACULATED AND CAPACITATED SPERMATOZOA

PDC-109 (13 kDa) is the most abundant component, and the major heparin -binding protein, of bovine (Bos taurus) seminal plasma. Here, we show that PDC-109 contains a single O-linked oligosaccharide (NeuNAc alpha (2-6)-Gal beta(1-3)-GalNAc-) attached to Thr(11). Immunoquantitation o f PDC-109 indicates that its concentration in seminal plasma is 15-20 mg/ml. Though PDC-109 is not present on epididymal sperm, ejaculated s permatozoa on average are coated with (9.5 +/- 0.3) x 10(6) molecules of PDC-109/cell. This value remained constant in swim-up sperm and dec reased to (7.7 +/- 0.4) x 10(6)/spermatozoon after incubation for 24 h in capacitation medium at 39 degrees C. These data substantiate the h ypothesis that PDC-109 may be one of the seminal plasma components tha t enhance the fertilizing capacity of bull spermatozoa upon interactio n with heparin-like glycosaminoglycans present in the female genital t ract.