Characteristics of selected seminal plasma proteins and their application in the improvement of the reproductive processes in mammals: Understanding the biochemical processes associated with ovum fertilization and knowledge about the structure and function of individual substances participating in these processes is crucial for the development of biotechnological methods to improve reproduction of animals and humans. Among many components of seminal plasma, proteins and peptides play a specific role in regulation of the fertilization process, particularly through their ability to bind various types of ligands such as polysaccharides, lipids and ions. Heparin-binding proteins regulate capacitation and acrosome reaction processes. Affinity of plasma proteins to mannans of the fallopian tube epithelium facilitates formation of spermatozoa reservoirs in the female reproductive tract. Ability to bind phosphorylcholine is one of the conditions for the coating of the seminal plasma proteins on the sperm membrane and also determines the formation of oligomeric forms of certain proteins. Zinc binding by seminal plasma proteins regulates sperm chromatin condensation state. It also affects motility of these cells and acrosome reaction. The interspecies analysis indicates significant structural and functional similarities, especially for the proteins with low molecular weight. Fertility associated proteins (FAPs) have been determined in the bull, stallion, boar, ram and dog. The contents of these proteins correlate with the indicators of the fertilizing abilities of sperm. In humans, several seminal plasma proteins were found which serve as diagnostic markers of spermatogenesis, seminiferous epithelium state, and azoospermia. To determine the semen ability for preservation, measurement of some seminal plasma protein content may also be used. Addition of specific plasma proteins to a spermatozoa solution undergoing the process of preservation may be used to retain the features of the cells responsible for efficient fertilization.

Affinity chromatography on Chelating Sepharose Fast Flow Gel-Zn(2+) was used for fractionation of boar seminal plasma proteins. Approximately 30% of total boar seminal plasma proteins showed affinity for zinc ions (ZnBP fraction). Native electrophoresis (PAGE) of ZnBP revealed six protein fractions which separated into 27 bands under denaturing conditions (SDS/PAGE). Two-dimensional electrophoresis (2D PAGE) showed 148 polypeptides with isoelectric points mostly in the basic and neutral pH range. The zinc-binding proteins comprise mainly 10-20 kDa polypeptides which are probably members of the spermadhesin family. ZnBP present in the incubation mixture of spermatozoa stored for 1 or 24 h at 4 °C allowed preservation of a higher percentage of cells exhibiting linear motility in comparison to a control sample stored in PBS. Presented results indicate that proteins binding Zn(2+) ions have a shielding effect on the sperm plasma membrane and acrosome of spermatozoa, protecting these structures against consequences of cold shock.