Effect of glycosylation on the heparin-binding capability of boar and stallion seminal plasma proteins.

Boar and stallion seminal plasmas were fractionated using affinity chromatography on heparin-Sepharose. In both species, among other proteins, the heparin-binding (H+) and non-heparin-binding (H-) fractions each contained glycoforms of either porcine PSP-I or equine HSP-1 and HSP-2. However, porcine H+/PSP-I eluted as a monomeric protein, whereas H-/PSP-I formed a heterodimer with PSP-II, another major seminal plasma protein. On the other hand, the stallion proteins H+/HSP-1 and H+/HSP-2 eluted together as an aggregate of relative molecular mass (M(r)) 90,000, whereas H-/HSP-1 and H-/HSP-2 eluted as monomers (15,000). Remarkably, when PSP-I and PSP-II from the H- fraction were separated, both proteins bound to heparin. Altogether these data show that glycosylation has an indirect effect on the heparin-binding ability of PSP-I, HSP-1 and HSP-2 through modulation of their aggregation state.