Zinc-binding proteins from boar seminal plasma-isolation, biochemical characteristics and influence on spermatozoa stored at 4 °C

Abstract

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.