Problem: Boar seminal plasma contains various types of proteins. Most of them belong to spermadhesins and some of them contain fibronectin type II domain. Almost all of these proteins are present under physiological conditions in aggregated forms differing in their relative molecular mass, composition, and binding properties. The study of mutual specific interactions between proteins of boar seminal plasma that could be involved in the formation of aggregated forms and most probably of sperm coating layers is the subject of our present communication.
Methods of study: Aggregated forms of boar seminal plasma proteins separated by size exclusion chromatography were analysed by Reversed-phase High-performance Liquid Chromatography (RP HPLC), SDS-PAGE and immunochemical methods (ELISA and immunoblotting). Mutual interactions between proteins were investigated by size exclusion chromatography of a mixture of separated monomer proteins and affinity chromatography of boar seminal plasma on immobilized spermadhesins.
Results: Composition of proteins that are adsorbed from boar seminal plasma to immobilized spermadhesins corresponds to that of aggregated forms found in seminal plasma. Mutual interactions between monomer forms observed by size exclusion chromatography are in good agreement with results of affinity chromatography. An existence of interactions between spermadhesins of the AQN and AWN families and the DQH sperm surface protein, as well as between proteins involved in the formation of heterodimer porcine seminal plasma I (PSP I)/PSP II was proved.
Conclusion: Mutual specific interactions between protein components of boar seminal plasma were shown. These interactions participate in the formation of aggregated forms of proteins in seminal plasma and probably also in the arrangement and remodelling of protein coating layers of sperm. Aggregation of seminal plasma proteins is probably an important phenomenon in the fertilization process.